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Fibrillin-2 (FBN2) mutations result in the Marfan-like disorder, congenital contractural arachnodactyly.

Congenital contractural arachnodactyly (CCA) is an autosomal dominant disorder that is phenotypically similar to Marfan syndrome (MFS) and characterized by arachnodactyly, dolichostenomelia, scoliosis, multiple congenital contractures and abnormalities of the external ears. In contrast to MFS, CCA does not affect the aorta or the eyes. Two closely related genes, FBN1 located on chromosome 15q15-21.3 and FBN2 located at 5q23-31, encode large fibrillin proteins found in extracellular matrix structures called microfibrils. The MFS is caused by mutations in FBN1, while CCA has been genetically linked to FBN2 (refs 2, 5, 6). We now describe a pair of FBN2 missense mutations in two CCA patients that cause substitution of distinct cysteine residues in separate epidermal growth-factor-like (EGF) repeats. Our study provides final proof of the association between FBN2 mutations and CCA pathology, thus establishing the role of the fibrillin-2 in extracellular matrix physiology and pathology.

Base Sequence↗

Induction of skeletal muscle contracture and calcium release from isolated sarcoplasmic reticulum vesicles by sanguinarine.

The benzophenanthrine alkaloid, sanguinarine, was studied for its effects on isolated mouse phrenic-nerve diaphragm preparations. Sanguinarine induced direct, dose-dependent effects on muscle contractility. Sanguinarine-induced contracture was partially inhibited when the extracellular Ca(2+) was removed or when the diaphragm was pretreated with nifedipine. Depletion of sarcoplasmic reticulum (SR) internal calcium stores completely blocked the contracture. Sanguinarine induced Ca(2+) release from the actively loaded SR vesicles was blocked by ruthenium red and dithiothreitol (DTT), consistent with the ryanodine receptor (RyR) as the site of sanguinarine action. Sanguinarine altered [(3)H]-ryanodine binding to the RyR of isolated SR vesicles, potentiating [(3)H]-ryanodine binding at lower concentrations and inhibiting binding at higher concentrations. All of these effects were reversed by DTT, suggesting that sanguinarine-induced Ca(2+) release from SR occurs through oxidation of critical SH groups of the RyR SR calcium release channel.

Alkaloids↗

Prenatal ultrasound findings in a fetus with congenital contractural arachnodactyly.

Congenital contractural arachnodactyly (CCA) or Beals-Hecht syndrome is an autosomal dominant disorder caused by mutations in the fibrillin-2 (FBN2) gene. The principal features of CCA are a marfanoid habitus, multiple congenital contractures, camptodactyly, arachnodactyly, kyphoscoliosis, muscular hypoplasia, and external ear malformations. Our case is the first that shows typical sonographic signs in a fetus at 25 weeks' gestation with molecular genetically verified CCA in a large family with many members affected over four generations. This demonstrates that CCA can be detected prenatally by non-invasive ultrasonography. The importance of confirmation of CCA by means of DNA sequence analysis of the FBN2 gene is stressed.

Adult↗

Combined method of free lateral leg perforator flap with cervicoplasty for reconstruction of anterior cervical scar contractures: a new flap.

Anterior cervical scar contracture remains a challenging problem for the plastic surgeon. Recent advances in flap techniques have made it possible to transfer various kinds of autogenous tissue. A free lateral leg perforator flap (LLPF) was first introduced and developed to reconstruct this burn deformity, according to the special nature of perforator anatomy. The authors used this flap to resurface post-burn anterior cervical contracture in a 31-year-old female patient with second-to-third-degree flame burns. The size of the excised scar was 25 x 5.5 cm; the size of the flap was 22 x 8 cm, with total flap survival. The hospital stay was 9 days, and the donor site was covered with a split-thickness skin graft. After a 5-month follow-up, functional improvement was evaluated by an increase in extension of 33 degrees (preoperative 92 to postoperative 125 degrees); an increase in rotation of 15 degrees (preoperative 70 to postoperative 85 degrees); and an increase in lateral flexion of 10 degrees (preoperative 35 to postoperative 45 degrees). The cervicomandibular angle was improved by 20 degrees (preoperative 110 degrees to postoperative 90 degrees). Both functional and aesthetic results, including contour restoration, can be achieved, using this kind of perforator flap combined with cervicoplasty.

Adult↗

Congenital contractural arachnodactyly and femoral fracture in a newborn infant: a causal relationship or a coincidence?

Congenital contractural arachnodactyly (CCA, Beals syndrome) is an autosomal-dominant connective tissue disorder characterized by multiple flexion contractures, arachnodactyly, severe kyphoscoliosis, abnormal pinnae, and muscular hypoplasia. Although it is a connective tissue disorder affecting bone structure and formation, coexistence of bony fractures in CCA patients have not been reported before. In this article we report a newborn infant diagnosed with CCA who developed a femoral fracture possibly due to abnormal bone structure and birth injury in spite of cesarean delivery.

Adult↗

[A new emphasis on the diagnosis of malignant hyperthermia using the in vitro contracture test?].

In accordance with the protocol of the European Malignant Hyperpyrexia Group, an account is given of the experience regarding establishment of the "in vitro contracture test" for diagnosis and exclusion of malignant hyperpyrexia disposition at the University Clinic of Leipzig. Since its commencement in 1986 these diagnostic possibilities are being increasingly utilized, and--basing on 76 MH manifestations and suspected cases--324 persons have been examined until now. Besides the representation of the methodical features (e.g. performance of biopsy in tranquanalgesia in children), emphasis was on the safety of executing this test (attaining higher specificity, total absence of MH manifestations). The epidemiological study of the results shows the varying knowledge of physicians and the interference by insufficient investigation alternatives in individual areas. On the basis of the results, the use of the in vitro contracture test is recommended in all MH suspected cases by the authorized and qualified regional centres.

Adolescent↗

The pathogenesis of fetal hypokinesia. A neurological study of 75 cases of congenital contractures with emphasis on cerebral lesions.

A comprehensive prospective clinical study is presented of 75 cases of fetal hypokinesia and congenital contractures of various causes, with neuropathological investigation in 23 cases. With the data of medical history, neurological examination, laboratory tests and neuropathology an exact or probable nosological or syndromal diagnosis could be made in 61 cases. These cases were categorized by localisation of causal pathology in the subsequent levels of the developing motor system. In 14 of 61 cases developmental brain disorders (f.i. hydrocephalus, hydranencephaly, microcephaly) were the cause of fetal hypokinesia, often with perinatal death, whereas in 7 cases both cerebral and/or spinal cord lesions were found. Besides cerebral involvement was frequently present in cases with congenital contractures of other origin, concomitant or due to perinatal complications. In a large number of cases clinical evidence of spinal cord lesions, especially anterior horn cell degeneration was present. Myopathic disorders occurred in only four cases, whereas congenital myasthenia and congenital neuropathy were present in one case each. In cases without muscle weakness miscellaneous disorders including congenital skin anomalies and probably primary connective tissue disorders were encountered. The etiologic role of intrauterine viral infection is discussed.

Adolescent↗

Decreased tetanic contracture of rat skeletal muscle induced by pyridostigmine.

The purpose of this study was to compare the effects of various regimens of pyridostigmine administration on the contractile strength of skeletal muscle. Rats were exposed to pyridostigmine according to 3 dosing schedules: 2 mg/kg ip daily, 5 mg/kg X d by sc infusion, and 25 mg/kg X d by sc infusion. After 1, 4, 10, and 20 d of exposure, measurements were made of muscle tension during tetanic stimulation, and of muscle mass, erythrocyte acetylcholinesterase activity, and body weight. Pyridostigmine produced a dose-dependent decrement in the contracture generated during tetanic stimulation. Peak effect was observed after 4 d of exposure but remained depressed after 20 d. The magnitude of the decrement correlated with the frequency of the tetanic stimulation (from 20 to 100 Hz). Muscle tension at the end of the tetanic stimulus was affected to a greater extent than the initial tension. The 25-mg/kg infusion of pyridostigmine significantly depressed erythrocyte acetylcholinesterase activity throughout the study and also decreased body weight on d 1-4. No change in muscle mass was observed in any treatment group. These results show that pyridostigmine exposure results in decrements in skeletal muscle contracture that are dose-dependent, frequency-dependent, and time-dependent. The effect is probably not the result of muscle wasting and does not correlate well with erythrocyte acetylcholinesterase inhibition. The results are consistent with effects of pyridostigmine, both presynaptically and postsynaptically, at the neuromuscular junction that affect neurotransmitter release and receptor responsiveness.

Acetylcholinesterase↗

The influence of ionic strength on potassium contractures and calcium movements in frog muscle.

Frog toe muscles were bathed in isotonic, sodium-free Tris chloride, methanesulfonate, or sulfate solutions containing sucrose or mannitol and varying in ionic strength from 0.006 to 0.291. By decreasing the ionic strength the curve relating the peak tension of the K contractures to the log [K] was reversibly shifted to lower [K]. Increasing the [Ca] from 1 to 4 mM almost abolished this effect. The resting uptake of (45)Ca was increased more than two times by decreasing the ionic strength from 0.125 to 0.039. It was not increased significantly by raising [Ca] from 1 to 4 mM at low or normal ionic strength. The additional uptake of (45)Ca during contractures provoked by 120 mM K was not significantly different at the two levels of ionic strength. The rate of emergence of (45)Ca from muscles loaded with (45)Ca at reduced ionic strength, was decreased. The effects of low ionic strength are discussed in terms of changes in the potential difference across a membrane with fixed negative charges on the outer surface.

Animals↗

The relationship between caffeine contracture of intact muscle and the effect of caffeine on reticulum.

At concentrations between 1 to 10 mM, caffeine reduced the Ca-accumulating capacity of fragmented reticulum obtained from frog and rabbit muscle. With 8 mM caffeine enough Ca was released from frog reticulum to account for the force of the contracture. Caffeine did not affect all reticulum membranes equally. The fraction which was spun down at 2000 g was more sensitive than the lighter fractions. The percentage of the total accumulated Ca released by caffeine decreased with decreasing Ca content of the reticulum. In parallel with their known effects on the caffeine contracture, a drop in temperature increased the caffeine-induced Ca release while procaine inhibited it. Caffeine also inhibited the rate of Ca uptake, which may in part account for the prolongation of the active state caused by caffeine.

Animals↗

Prenatal diagnosis in congenital contractural arachnodactyly.

Congenital contractural arachnodactyly (CCA) is a heritable connective tissue disorder caused by defects in the gene encoding fibrillin-2 (FBN2). People with CCA typically have a marfanoid habitus, flexion contractures, severe kyphoscoliosis, abnormal pinnae, and muscular hypoplasia. Because of the relative infrequency of the syndrome and its generally mild to moderate severity, prenatal diagnosis had not previously been sought. Here we report prenatal diagnosis in a family with CCA. Because the course of the disease in the proband was rather severe, she had requested genetic counseling as early as age 17. She delayed childbearing until prenatal diagnosis for CCA became possible. This decision was supported by her mother and later her husband. Because she shared the same genotype with her husband, genetic linkage analysis of this family did not alter the a priori 50% risk of having an affected child. The possibility of unambiguously ascertaining the affected status of a fetus homozygous for the tested FBN2 marker was sufficient for the family to pursue prenatal diagnosis. This case strongly points to the importance of informed decisions now that genetic testing is becoming commonplace.

Adult↗

Suxamethonium-induced muscle contracture following traumatic denervation in man.

The effects of the systemic and of the i.v. regional administration of suxamethonium were investigated in 23 patients with traumatic nerve injury. Following the systemic administration of suxamethonium 100 mg, normally innervated muscles showed muscle fasciculations initially, followed by muscular relaxation. On the other hand, denervated muscles did not fasciculate and, in 21 patients, manifested suxamethonium-induced contractures. In the other two patients no response was observed. In 10 of the patients, the i.v. regional administration of suxamethonium 5 mg was followed by a contracture of the denervated muscle which was maintained until the tourniquet was deflated. No systemic reaction to suxamethonium, other than mild ptosis, followed the release of the tourniquet.

Humans↗

Viability criterion of muscle bundles used in the in vitro contracture test in patients with neuromuscular diseases.

We have compared the viability criteria of muscle bundles used in the in vitro contracture test for susceptibility to malignant hyperthermia (MH) in a group of 28 patients with various neuromuscular diseases (NMD) and 93 MH-related family patients. In the patients with NMD, this standard test gave one positive, six equivocal and 21 negative results. Compared with MH-related family patients, muscle bundles used had significantly smaller resting membrane potentials and smaller predrug twitch tension amplitudes. Some results from the group with NMD were obtained with muscles which were damaged, more rapidly deteriorating, non-standard or both, and should not be taken to indicate that the patients have the genetic trait for MH. The in vitro contracture test is not always relevant for myopathic muscle (especially dystrophic muscle) and this could explain the lack of specificity for MH.

Caffeine↗

Effect of different volatile anaesthetics on suxamethonium-induced jaw muscle contracture in rats.

Previous work has demonstrated that the interaction of hyperthermia and halothane may greatly increase the jaw muscle contracture produced by suxamethonium. We have compared the interaction of temperature and suxamethonium in the presence of halothane with the suxamethonium/temperature interaction of two other volatile anaesthetics, isoflurane and desflurane. Rats were anaesthetized with 1.35 MAC of halothane, isoflurane or desflurane. The jaw area was heated to 36-41 degrees C by a heating lamp while rectal temperature was maintained at 37 degrees C. Isometric tension was recorded from the jaw muscles. Suxamethonium 750 micrograms kg-1 i.v. induced a transient jaw muscle contracture (JMC) during halothane, isoflurane and desflurane anaesthesia. JMC exhibited significant dependence on jaw muscle temperature with all three volatile anaesthetics. Increasing the temperature of the jaw area from 37 degrees C to 41 degrees C increased JMC 8.7-fold with halothane, 8.8-fold with isoflurane and 3.1-fold with desflurane. The difference between halothane and desflurane was significant. While suxamethonium-induced JMC was dependent on temperature for all three volatile anaesthetic, the temperature dependence appeared to be less with desflurane.

Anesthetics↗

Antagonism of suxamethonium-induced jaw muscle contracture in rats.

Masseter muscle rigidity (MMR) induced during general anaesthesia by suxamethonium is a clinical problem that may interfere with tracheal intubation. We have investigated the relation between twitch tension and contracture response to suxamethonium in rats. Rats were anaesthetized with 1% halothane (1.35 MAC). Jaw muscle temperature was maintained at either 37 or 41 degrees C while rectal temperature was kept at 37 degrees C by radiant heat. Twitch tension was produced by nerve stimulation at 0.2 Hz. Rats were pretreated with either a low dose of vecuronium (0.03 mg kg-1) or dantrolene (0.8 mg kg-1). Thereafter suxamethonium 750 micrograms kg-1 was administrated i.v. Low-dose vecuronium pretreatment significantly (90%) decreased suxamethonium-induced jaw muscle contracture (JMC) with minimal (3%) twitch block during local hyperthermia. Low-dose dantrolene pretreatment also reduced JMC (81% at 37 degrees C and 82% at 41 degrees C) while decreasing twitch by 30% at 37 degrees C and 31% at 41 degrees C. Both vecuronium and dantrolene at doses that minimally depressed the twitch response antagonized suxamethonium-induced JMC. We speculate that pretreatment with low-dose vecuronium decreases suxamethonium-induced MMR clinically.

Animals↗

Anaerobic glycolysis and the development of ischaemic contracture in isolated rat heart.

The relationship between myocardial ATP content and the increase in left ventricular resting tension during ischaemia (ischaemic contracture) was studied in isolated rat hearts perfused for 15 min either with aerobic buffer (pO2 greater than 500 mmHg) containing non-glycolytic substrate, acetate (5 mmol X litre-1), or with hypoxic buffer (pO2 less than 10 mmHg) with glucose (10 mmol X litre-1) before making them totally ischaemic for 10 min. ATP was determined spectrophotometrically from extracts of frozen whole hearts. Left ventricular tension was recorded by intraventricular balloon catheter. Myocardial ATP content was 15.4 +/- 1.0 mumol X g-1 dry weight (mumol X g-1) after 10 min stabilising period, 14.1 +/- 0.9 mumol X g-1 after 15 min aerobic perfusion (plus acetate) and 9.0 +/- 1.3 mumol X g-1 after 15 min hypoxic perfusion (plus glucose). During 10 min of ischaemia ATP decreased in aerobic hearts to 5.4 +/- 1.1 mumol X g-1 and to 7.9 +/- 1.0 mumol X g-1 in hypoxic hearts. The left ventricular resting tension increased during ischaemia in hypoxic hearts to 9 +/- 5% of control systolic pressure (0 = diastolic pressure, 100 = systolic pressure during stabilising period), whereas in aerobic hearts the tension began to increase immediately and was 84 +/- 22% of systolic pressure at the end of the ischaemic period. In parallel control experiments, hearts were also perfused either with glucose-containing aerobic buffer or acetate-containing hypoxic buffer. ATP was well preserved during aerobic perfusion (plus glucose) but decreased markedly during hypoxic perfusion (plus acetate). There was no increase in resting tension in the aerobic hearts (plus glucose) whereas the resting tension increased considerably during hypoxic perfusion (plus acetate). The results indicate that the initiation of ischaemic contracture occurs at much higher myocardial ATP level when ATP comes from mitochondrial sources than when ATP is generated by anaerobic glycolysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetates↗

Timing of the switch from myometrial contractures to contractions in late-gestation pregnant rhesus monkeys as recorded by myometrial electromyogram during spontaneous term and androstenedione-induced labor.

Pregnant rhesus monkeys were studied to determine the precise time in relation to photoperiod of the onset, and the nature, of the switch in myometrial activity patterns from contractures to contractions. We investigated both spontaneous term labor and androstenedione-induced preterm labor. Under general anesthesia at 127 +/- 2 days gestation (dGA) (mean +/- SEM), 16 pregnant rhesus monkeys were instrumented with maternal femoral arterial and venous catheters and myometrial electromyogram electrodes. Eight animals (group I) received continuous i.v. infusion of intralipid (n = 7) or saline (n = 1) that was started at 143.3 +/- 2 dGA and maintained until the spontaneous onset of term labor. Nine animals (group II) received continuous i.v. infusion of androstenedione that was started at 139 +/- 0.4 dGA and maintained until the onset of prematurely induced labor. Myometrial activity was recorded continuously. All monkeys in both groups demonstrated nocturnal switches in myometrial activity from contractures to contractions. The mean time of onset of the switch in group I and group II monkeys was similar, occurring at 0.7 +/- 0.4 h or 0.8 +/- 0.5 h, respectively, after the onset of darkness. Group II monkeys demonstrated greater regularity in both the time of onset and the repetitive occurrence each night once the switch occurred, as well as greater consistency in duration in their switch patterns, than did group I monkeys.

Androstenedione↗

Caffeine and halothane contracture testing in swine using the recommendations of the North American Malignant Hyperthermia Group.

Caffeine and halothane contracture testing is widely used to detect malignant hyperthermia (MH) susceptibility. The accuracy and reliability of the 3% halothane test and the incremental caffeine test, as recommended by the North American MH Group, were assessed in 11 swine (five MHS, six control). Nine swine were tested twice, 4-6 weeks apart. Accuracy of the in vitro diagnosis was also assessed by in vivo anesthetic challenge. Of all muscle bundles from MH-susceptible swine, 65% reacted positively to 3% halothane and 70% to 2 mM caffeine. Only 35% had a positive caffeine-specific concentration, and 25% developed an increase in baseline tension greater than or equal to 7% at 2 mM caffeine. However, when only the most positive response to 3% halothane or to 2 mM caffeine was used (a minimum of three fresh muscle strips is recommended), these two tests were highly sensitive and specific. In control swine one of 30 muscle bundles reacted positively to 3% halothane. A positive caffeine-specific concentration developed in one of 25 control muscle bundles exposed to caffeine. The variability in the results of these tests mandated that at least three muscle bundles be used for each test. Nonviable muscle bundles could not be relied upon to provide accurate results. In this porcine model, MH susceptibility could be detected by performing the Caffeine Halothane Contracture Test (CHCT) according to the guidelines of the North American MH Group. However, only the 3% halothane test and the response to 2 mM caffeine produced adequate diagnostic results in this breed of swine.

Animals↗