1. Single muscle fibres were enzymatically isolated from the soleus and extensor digitorum longus (EDL) muscles of genetically
dystrophic mdx and normal (C57BL/10) mice aged 3-6 or 17-23 weeks. 2. ...Fibres of both muscles were chemically skinned with
the non-ionic detergent Triton X-100 (2% v/v). Ca(2+)- and Sr(2+)-activated contractile responses were recorded and comparisons
were made between several contractile parameters of various fibre types of normal and dystrophic mice of similar age. 3. There
were no significant differences in the following contractile parameters of skinned fibres of normal and mdx mice of the same
age: sensitivity to activating Ca2+ (pCa50) or Sr2+ (pSr50) and differential sensitivity to the activating ions (pCa50-pSr50).
However the maximum isometric tension (Po) and the frequency of myofibrillar force oscillations in EDL fast-twitch fibres
of young mdx mice were significantly lower than those of soleus fast-twitch fibres of the same animals, or fast-twitch fibres
(EDL or soleus) of normal mice. 4. Age-related differences were apparent in some contractile parameters of both normal and
mdx mice. In particular the steepness of force-pCa and force-pSr curves increased with age in normal mice, yet decreased with
age in fibres of mdx mice. 5. A fluorescent probe, ethidium bromide, which interchelates with DNA, was used with laser-scanning
confocal microscopy to determine the distribution of myonuclei in fibres. Fibres isolated from either muscle type of normal
animals displayed a characteristic peripheral spiral of myonuclei. Fibres from muscles of mdx mice displayed three major patterns
of nuclear distribution; the normal peripheral spiral, long central strands of nuclei, and a mixture of these two patterns.
6. The contractile characteristics of mdx fibres were not markedly influenced by the nuclear distribution pattern in that
there were no discernible differences in the major contractile parameters (the Hill coefficients nCa and nSr, which are associated
with the steepness of the Ca2+ and Sr2+ activation curves, pCa50, pSr50, pCa50-pSr50) of skinned fibres possessing peripheral
or central nuclei. However, except for nSr, these values were all lower in individual fibres which displayed similar proportions
of central and peripheral nuclei. The presence of mixed nucleation and absence of fibres with embryonic contractile characteristics
in mdx mice suggest that the dystrophin-negative fibres can repair locally occurring muscle damage.
1 Department of Physiology,
University of Western Australia, Nedlands 6907;
2 School of Physiology and
Pharmacology, University of New South Wales, Sydney 2052;
4 School of Zoology, La Trobe
...University, Bundoora 3083, Australia; and
3 Division of Neuroscience,
School of Biological Sciences, University of Manchester, Manchester M13
9PT, United Kingdom
We examined the effect of the
2 -agonist clenbuterol (50 µM)
on depolarization-induced force responses and sarcoplasmic reticulum (SR) function in muscle fibers of the rat ( Rattus
norvegicus ; killed by halothane overdose) that had been
mechanically skinned, rendering the
2 -agonist pathway inoperable.
Clenbuterol decreased the peak of depolarization-induced force
responses in the extensor digitorum longus (EDL) and soleus fibers to
77.2 ± 9.0 and 55.6 ± 5.4%, respectively, of
controls. The soleus fibers did not recover. Clenbuterol significantly
and reversibly reduced SR Ca 2+
loading in EDL and soleus fibers to 81.5 ± 2.8 and 78.7 ± 4.0%, respectively, of controls. Clenbuterol also produced
an ~25% increase in passive leak of
Ca 2+ from the SR of the EDL and
soleus fibers. These results indicate that clenbuterol has direct
effects on fast- and slow-twitch skeletal muscle, in the absence of the
2 -agonist pathway. The
increased Ca 2+ leak in the triad
region may lead to excitation-contraction coupling damage in the soleus
fibers and could also contribute to the anabolic effect of clenbuterol
in vivo.
calcium uptake; calcium leak; calcium release; -agonist; excitation-contraction coupling; anabolism
Background. Headache is a common problem in primary care. Although most patients are treated by GPs, many are referred to specialist consultation. Knowledge of how the referrals can be improved is ...therefore an important issue. Objectives. The aim of this study was to determine the relationship between self-initiating referral to a neurologist and the patient's satisfaction with the specialist consultation. Methods. All patients who had been examined by a neurologist for headache within a 2-year period from three neurological centres in North Norway completed a questionnaire. Results. A total of 1052 patients from a population of 1403 headache patients (75%) returned the questionnaire while 927 patients answered questions about initiating the referral to the specialist. Two hundred and twenty patients (24%) initiated the referral to the neurologist themselves; 52% of those who self-initiated the referral were dissatisfied with the specialist consultation compared with 42% of those referred by the doctor, P = 0.002. Chronic headache, tension-type headache (TTH) and daily use of analgesic drugs were associated with dissatisfaction. Conclusions. Patients with headache who initiated the referral to a neurologist themselves were less satisfied with the specialist consultation. Selecting referrals containing proper medical information may improve satisfaction in severe headache patients treated in a neurological practice.
1. Single, intact muscle fibres were dissociated enzymatically from skeletal muscles of phenotypically normal (+/?) and dystrophic
mice (129/ReJ dy/dy: Dystrophia muscularis), and resting Ca2+ levels ...were measured by image analysis of intracellular Fura-2
fluorescence in distinct parts of the fibres. 2. Fura-2 was introduced into fibres by ionophoresis with glass microelectrodes
to concentrations of between 50 and 200 microM. Over this concentration range there was no apparent buffering of intracellular
Ca2+ by Fura-2. 3. Fibres isolated from the soleus, flexor digitorum brevis (FDB) and extensor digitorum longus (EDL) muscles
of normal animals maintained resting Ca2+ of 106 +/- 2 nM. Ca2+ distributions within individual fibres were homogeneous.
4. Fibres from dystrophic animals maintained Ca2+ that was elevated two- to fourfold in comparison to normal fibres. 5.
The population of skeletal fibres from dystrophic mice which displayed morphology similar to that of fibres of normal animals
were found to have Ca2+ levels that averaged 189 +/- 2 nM. The distribution of Ca2+ within these fibres appeared uniform.
6. The population of dystrophic fibres that possessed morphological abnormalities maintained even higher Ca2+ concentrations
(368 +/- 3 nM). Several fibres from this morphological group displayed obvious heterogeneity in Ca2+ distribution with distinct,
localized areas of higher Ca2+. 7. These results support the contention that Ca2+ homeostasis is markedly impaired in dystrophic
muscle. The elevated Ca2+ levels are near the threshold for contraction and, together with severe morphological fibre abnormalities,
are probably centrally involved in fibre necrosis apparent in muscular dystrophy.
The mdx (muscular dystrophy X-linked) mouse is a model for human Duchenne muscular dystrophy (DMD) and is characterized by the absence of the cytoskeletal protein dystrophin. Using a cerebellar slice ...preparation, we show that postsynaptically mediated long-term depression (LTD) is significantly reduced in mdx Purkinje cells, while presynaptically mediated paired-pulse facilitation (PPF) is normal. This disruption of LTD could contribute to the cognitive deficit in boys with Duchenne muscular dystrophy.
This study investigated the effects of the protein kinase A (PKA) inhibitor, H-89, in mechanically-skinned muscle fibres and intact muscle fibres, in order to determine whether PKA phosphorylation is ...essential for normal excitation-contraction (E-C) coupling. In skinned EDL fibres of the rat, force responses to depolarization (by ion substitution) were inhibited only slightly by 10 microM H-89, a concentration more than sufficient to fully inhibit PKA. Staurosporine (1 microM), a potent non-specific kinase inhibitor, also had little if any effect on depolarization-induced responses. At 1-2 microM, H-89 significantly slowed the repriming rate in rat skinned fibres, most likely due to it deleteriously affecting the T-system potential. With 100 microM H-89, the force response to depolarization by ion substitution was completely abolished. This inhibitory effect was reversed by washout of H-89 and was not due to block of the Ca2+ release channel in the sarcoplasmic reticulum (SR). In intact single fibres of the flexor digitorum longus (FDB) muscle of the mouse, 1-3 microM H-89 had no noticeable effect on action-potential-mediated Ca2+ transients. Higher concentrations (4-10 microM) caused Ca2+ transient failure in fibres stimulated at 20 Hz in a manner indicative of action-potential failure. At 10-100 microM, H-89 also inhibited net Ca2+ uptake by the SR and affected the Ca2+-sensitivity of the contractile apparatus in rat skinned fibres. All such effects were proportionately greater in toad muscle fibres. These results do not support the hypothesis that phosphorylation is essential for the Ca2+ release channel to open in response to voltage-sensor activation in skeletal muscle fibres.
Duchenne muscular dystrophy (DMD) is caused by the absence of a functional transcript of the protein dystrophin. DMD is associated with a range of cognitive deficits that are thought to result from a ...lack of the protein dystrophin in brain structures involved in cognitive functions. The CNS involvement extends to an impairment of cognitive abilities, with many DMD boys having significant reduction in IQ. In the cerebellum, dystrophin is normally localized at the postsynaptic membrane of GABAergic synapses on Purkinje cells. Here, we investigate the effect of an absence of dystrophin on the number of GABA sub(A channels located at the synapse in cerebellar Purkinje cells of the dystrophin-deficient mdx mouse. Whole-cell patch-clamp recordings of spontaneous miniature inhibitory postsynaptic currents (mIPSCs) were performed in cerebellar slices from mdx and littermate control mice. Our results showed that the number of receptors at GABAergic synapses in the cerebellar Purkinje cell was significantly reduced in mdx mice (38.38 +/- 2.95) compared to littermate controls (53.03 +/- 4.11). Furthermore, when gaboxadol was added to the bath, the change in holding current in mdx mice was significantly enhanced (65.01 +/- 5.89 pA) compared to littermate controls (37.36 +/- 3.82 pA). The single channel unitary conductance and the rise and decay time of mIPSCs were not significantly different in these two groups of mice, indicating that those GABA) sub(A) channels located at the postsynaptic sites in the mdx mice function normally. Conclusion: There is a reduction in the number of functional receptors localized at GABAergic synapses in the cerebellar Purkinje cells of dystrophin-deficient mdx mice and an increase in a gaboxadol induced holding current, which is evidence for an increase in extrasynaptic GABA sub(A receptors in mdx mice. We hypothesize that the absence of dystrophin, from mdx Purkinje cells, reduces the number of post-synaptic GABA) sub(A) receptors and as a result there is an increase in extrasynaptic receptors. If similar changes occur in the CNS in boys with DMD, it will impact on the function of neural networks and may contribute to some of the motor, behavioral and cognitive impairment apparent in many boys with DMD.
Background: Elective treatment of the neck in oral squamous cell carcinoma has changed over the last 20 years. The main object of this report is to present the results of a multi-institutional ...prospective study designed to compare standard treatment with modified radical classical neck dissection (MRND) to supraomohyoid neck dissection (SOH) in the management of the clinically negative neck in oral cancer patients.
Patients and methods: A total of 148 patients were included in the trial. All patients had previously untreated T2 to T4 N0 squamous cell carcinoma of the oral tongue (62 cases), floor of the mouth (49 cases), inferior gingiva (12 cases), or retromolar trigone (25 cases). Tumor stages were T2, 91; T3, 27; and T4, 30. There were no significant imbalances between groups.
Results: The false-negative rate was 28%, and most positive nodes were sited at level II and III. Complications were seen in 41% of MRND patients and in 25% of SOH patients (
P = 0.043). Median total duration of hospitalization was 9 days in MRND patients and 7 days in the SOH group. To date, 19 and 16 patients presented with local and neck recurrences, respectively. The 60-month actuarial survival rates were 63% in the MRND group and 67% in the SOH group (
P = 0.7150).
Conclusions: This study demonstrates that the recurrence and survival rates were similar in both groups. SOH neck dissection can be recommended as standard elective treatment for patients with T2–T4 oral squamous cell carcinomas.
We investigated evoked EPSPs and spontaneous IPSPs in cerebellar slices from dystrophin-deficient
mdx mice. In the presence of the GABA
A antagonist bicuculline the increase in EPSP amplitude was ...less in
mdx Purkinje cells compared to control, and the amplitude of miniature IPSCs in
mdx cells was also significantly less than in controls. This reduced inhibitory input is most likely due to the reported reduction in the size of GABA
A channel clusters.
PDF
