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At least 1,621 records · Page 90Linked to original sources
PubMed2004

Effects of prednisone in canine muscular dystrophy.

Glucocorticoid use may provide short-term functional improvement in boys with Duchenne muscular dystrophy (DMD). We report functional and histopathologic changes following a 4-month course of daily oral prednisone in a canine model of DMD, termed golden retriever muscular dystrophy (GRMD). Muscle extension forces in GRMD dogs treated daily with 1 and 2 mg/kg prednisone measured 2.349 +/- 0.92 and 3.486 +/- 0.67 N/kg, respectively, compared to 1.927 +/- 0.63 N/kg in untreated GRMD controls (p < 0.05 for 2 mg/kg group); GRMD muscle flexion forces measured 0.435 +/- 0.13 and 0.303 +/- 0.08 N/kg, respectively, compared to 0.527 +/- 0.01 N/kg in untreated GRMD controls (p < 0.05 for both groups). Although cranial sartorius hypertrophy and tibiotarsal joint angles also tended to improve, myofiber calcification increased and fetal myosin expression decreased following prednisone. Thus, functional data indicate benefit but histopathologic changes following prednisone treatment in GRMD suggest possible deleterious consequences.

Animals↗
PubMed1986

Effects of several antibiotics on the neuromuscular junction: Part II.

The effects of various kinds of antibiotics including tetracycline (TC), chloramphenicol (CP), sodium cephalothin (CET), sodium cefazolin (CEZ), colistin sulfate (CL), colistin sodium methanesulfonate (CL-M), bacitracin (BC), gramicidin HCl (GR), rifampicin sulfate (RFP) and lincomycin (LCM), on the neuromuscular junction (NMJ) were studied by in vitro and in vivo experiments. In in vitro experiments, CL and LCM exhibited a blocking effect on the NMJ in rat phrenic nerve diaphragm preparations, and GR caused a marked increase in muscle contraction. This effect was not affected by administration of eserine or CaCl2. In in vitro experiments with frog sciatica nerve and musculus sartorius preparations, CL and GR induced the appearance of endplate potentials, suggesting blockade of the NMJ. No blocking effect of other antibiotics was observed. In in vitro experiments with the preparations from Rana catesbiana frogs, TC and LCM induced a decrease in the frequency of miniature endplate potentials. In in vivo experiments with rabbit musculus tibialis anterior preparations, CL, TC and LCM exerted a blocking effect soon after administration, but GR and RFP had a late blocking effect. CL, GR, BC and RFP were found not to compete with eserine or CaCl2 in terms of the blocking effect on the NMJ. From the fact that TC did not compete with eserine but did compete with CaCl2 and with KCl as blockers at the NMJ, this blocking effect of TC seems to be due to inhibition of release of acetylcholine (ACh). The fact that LCM competes with eserine indicates that this antibiotic has the same type of action as curare on ACh receptors of the NMJ.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1993

Dequalinium: a potent inhibitor of apamin-sensitive K+ channels in hepatocytes and of nicotinic responses in skeletal muscle.

The bisquaternary compound dequalinium has been tested for its ability to inhibit the loss of K+ which angiotensin II causes in guinea-pig hepatocytes and which occurs through apamin-sensitive Ca(2+)-activated K+ (SKCa) channels. Dequalinium blocked angiotensin II-evoked K+ loss with an IC50 of 1.5 +/- 0.1 microM and also inhibited 125I-monoiodoapamin binding with a KI of 1.1 +/- 0.1 microM. It is the most active non-peptide SKCa blocker so far described. The neuromuscular blocking agent vecuronium was also tested, and proved to be considerably less effective (IC50, 4.5 +/- 0.3 microM; KI, 3.6 +/- 0.5 microM). Dequalinium was also examined for its actions at nicotinic receptors in skeletal muscle and was found to be a potent, non-competitive antagonist of carbachol contractions of the frog rectus abdominis. In the frog cutaneous pectoris muscle, end-plate depolarizations induced by carbachol became smaller and more transient in the presence of dequalinium at 10 nM. However, contractions of the frog sartorius and rat diaphragm in response to nerve stimulation were inhibited only by concentrations > 1 microM. These apparently discrepant effects of dequalinium on nicotinic responses could be explained either by open channel block of slow onset or by 'stabilization' of the desensitized state of the receptor. The potency of dequalinium will make it a useful agent for the study of nicotinic receptors as well as of SKCa channels.

Angiotensin II↗
PubMed1988

Effects of dorsal bilateral rhizotomy treatment on transmitter systems in the spinal cord of normal and spastic dogs.

The high-affinity uptakes of [3H]serotonin, [3H]-glutamate, and gamma-[3H]aminobutyric acid were studied using a myelin-free crude synaptosomal fraction prepared from the spinal cords of normal dogs and spastic dogs following sham treatment or dorsal bilateral rhizotomy surgery. Compared to sham-operated controls, rhizotomy surgery of normal dogs produced, after 1 week, a 30% reduction in the Vmax value of [3H]glutamate, but did not alter the uptake of gamma-[3H]aminobutyric acid. This treatment also produced a 60% decrease in the Vmax value of [3H]serotonin. Comparison of the effect of rhizotomy surgery on normal and spastic dogs revealed that the spastic group had 60% higher Vmax values for uptakes of [3H]glutamate and gamma-[3H]aminobutyric acid. Comparison of sham-operated spastic dogs and rhizotomy-treated spastic animals showed that there was a 25% decrease in the uptake of both amino acids in the rhizotomy-treated spastic group. Overall, the data (a) support the hypothesis that glutamate is the neurotransmitter from some of the primary afferents, and (b) suggest that sprouting of interneuronal amino acid transmitter systems may occur in the spinal cords of spastic dogs.

Animals↗
PubMed1993

Effects of mescaline and some of its analogs on cholinergic neuromuscular transmission.

Mescaline (3,4,5-trimethoxyphenylethylamine; MES) and its analogs, anhalinine (ANH) and methylenemescaline trimer (MMT) were investigated, using sciatic-sartorius preparations of the frog and cortical tissue from the rat. The effects of MES and its analogs were examined with respect to muscle twitch, resting membrane potential and nicotinic receptor binding. Mescaline and its analogs (10-100 microM) blocked both directly and neurally evoked twitches but their effects on neurally evoked twitches were greater than those on directly evoked twitches. Mescaline, ANH and MMT decreased amplitude of the miniature endplate and endplate potentials, decreased acetylcholine (ACh) quantal content, hyperpolarized the resting membrane potential and prolonged duration of the action potential. They did not significantly displace the binding of [125I]-alpha-bungarotoxin (alpha-BTX) to nicotinic receptors, at concentrations which blocked neuromuscular transmission. These results suggest that MES and its analogs inhibit cholinergic neuromuscular transmission by blocking release of ACh; they also affect K+ conductance.

Acetylcholine↗
PubMed1976

[Effect of weak doses of ethyl alcohol on the resistance of the frog sartorius to injurious concentrations of that substance].

A study was made of the effect of preliminary maintenance of m. sartorius of the grass frog in 0.87 M and 1.09 M ethyl alcohol on their resistance to 3.48 M ethyl alcohol. The maintenance of muscle tissue in 0.87 M and 1.09 M ethyl alcohol for periods, ranging from 15 min. to 2 hours, in different series of experiments led to the increase in its resistance to 3.48 M alcohol by 11--24% as compared with the initial one. The value of increase in resistance depended on the concentration of the agent studied, the duration of maintenance, and of the season. A study of non-specificity of the adaptive effect of low alcohol decreased their resistance to 0.12 M NaF by 33.3% (P less than 0.05) The same concentration of ethyl alcohol applied for periods from 15 mintes to 2 hours either caused no change or decreased significantly the resistance of muscle tissue to the temperature 36 degrees C. This effect of decrease in resistance was even more significant when the resistance to 38 degrees C was challenged. The range of individual variability of resistance of muscles to 3.48 M alcohol and 36 degrees showns that its values in the control and in the experiment are similar.

Adaptation, Physiological↗
PubMed1994

A Danish family with limb-girdle muscular dystrophy with autosomal dominant inheritance.

We describe a Danish family of five generations showing a slowly progressive autosomal dominant limb-girdle myopathy with onset in early childhood. Three patients from two generations were examined and showed weakness predominantly of the proximal muscles of upper and lower extremities. Early contractures of wrist, tight heel cords, metacarpophalangeal and interphalangeal joints were present. Walking ability was partly preserved. Serum creatine kinase activity was normal or slightly elevated. EMG and biopsy showed mildly myopathic changes. Magnetic resonance images of the thigh showed severe atrophy of all compartments but with musculus semimembranosus, sartorius, and gracilis relatively preserved. This myopathy has a clinical picture similar to the Bethlem myopathy.

Biopsy↗
PubMed1996

Precision of reinnervation and synaptic remodeling observed in neuromuscular junctions of living frogs.

Repeated in vivo observations were used to study regenerated nerve terminals in neuromuscular junctions of the adult frog Rana pipiens. Sartorius junctions in living animals were stained with the fluorescent vital dye RH414 and viewed with video fluorescence microscopy. Each junction was observed in the intact muscle and then again 7, 10, and 13 weeks after nerve crush. At 13 weeks, junctions were determined to be mono- or polyneuronally innervated using intracellular recording. Between 7 and 13 weeks, most identified junctions were reinnervated less precisely and completely than described previously. Although some of the original synaptic gutters were reoccupied by regenerated terminal branches, other gutters were only partially occupied, and many appeared abandoned. Junctions showing precise recapitulation of original terminal arborizations comprised a small number of the total examined, as did those where reinnervation was very imprecise. Striking differences in the precision of reinnervation were found within the muscle such that distal terminals regenerated more precisely and completely than did proximal terminals. Terminals in reinnervated muscles were more dynamic than terminals in unoperated muscles over equivalent times. In singly innervated junctions, terminal growth was favored over regression. In doubly innervated junctions, regressive events were more common. Imprecise reinnervation is explained in terms of multisite innervation of muscle fibers and the activity dependence of synaptic stability. We hypothesize that when axons reinnervate the second or third junctions on a fiber, they do so less precisely, because the activity restored by reinnervation of the first junction renders later sites less attractive or less stable.

Animals↗
PubMed1984

In vitro O2 uptake and histochemical fiber type of resting hamster muscles.

In vitro oxygen consumption (VO2), histochemical fiber type, capillary arrangement, and muscle fiber geometry were measured in three hamster striated muscles. These muscles varied markedly in their histochemical fiber type composition (% by number): retractor (70% FG, fast-twitch, glycolytic; 16% FOG, fast-twitch, oxidative-glycolytic; 14% SO, slow-twitch, oxidative); soleus (57% FOG, 43% SO), and sartorius (98% FG, 2% FOG). Sartorius VO2 [0.80 +/- 0.034 (SE) ml O2 X min-1 X 100 g-1] was significantly different (P less than 0.01) from VO2 of retractor (0.89 +/- 0.038) and soleus (1.00 +/- 0.048). The number of capillaries around a fiber and the surface area/volume were greater for FOG and SO fibers than for FG fibers. Fibers of all types appeared to be roughly elliptical in shape. Capillaries were uniformly distributed around fibers in the soleus, but they were located more toward the ends of the major diameter in the retractor and sartorius. The results suggest a relationship among a fiber's oxidative capacity (based on its histochemical staining pattern), number of surrounding capillaries and surface area/volume. Furthermore, results suggest that VO2 and capillary spacing around a fiber may depend on fiber type.

Adenosine Triphosphatases↗
PubMedDate not supplied

The effect of imipramine on isolated skeletal muscle preparations.

Imipramine (2-10 microng/ml) noncompetitively inhibited acetylcholine responses of the frog rectus abdominis muscle, and markedly inhibited the contracture produced by carbachol and succinylcholine without affecting the contracture produced by KCl, caffeine, and chlorpromazine. The twitch responses to indirect and direct stimulation of the rat phrenic nerve-diaphragm and the frog sciatic nerve-gastrocnemius were first augmented and then depressed markedly and irreversibly by imipramine (5-20 microng/ml). The indirect stimulation was inhibited earlier and to a greater degree than the direct stimulation. The blockade in the nerve-sartorius developed and progressed quickly without prior augmented responses, and with a parallel time course for indirect and direct stimulation. On the frog rectus, physostigmine antagonised whereas d-tubocurarine and CaCl2 increased the imipramine-induced inhibition. In the nerve muscle preparations, physostigmine, CaCl2 and KCl did not affect the neuromuscular blockade produced by imipramine; tubocurarine (0.05 microng/ml) markedly increased the blocking effect of imipramine (20 microng/ml) on the rat phrenic nerve-diaphragm. The results have been discussed in relation to the memberane stabilizing and the calcium releasing actions of imipramine.

Acetylcholine↗