Hepatitis C is a global health problem caused by infection with the hepatitis C virus. Although representative prevalence data are not available from many countries, available data indicate that ...approximately 3% of the world’s population is infected with HCV. It is estimated that as many as 170 million persons worldwide may be infected with HCV. In many countries, the exact magnitude of the problem and the relative contribution of the various routes of transmission have not been defined with population‐based studies. Wherever possible such studies should be performed to enable countries to estimate the burden of hepatitis C disease, to prioritize their preventative measures and to make the most appropriate use of available resources. To assess hepatitis C on a global scale, the World Health Organization (WHO) organized a consultation of international experts, in order to review the public health aspects related to hepatitis C infection and to make recommendations for its prevention and control
1. Single intact muscle fibres were enzymatically isolated from the skeletal muscles of the dystrophic mouse 129/ReJ dy/dy
and were subjected to a range of physiological interventions. 2. ...Electrophysiological measurements, diffusion of injected
dyes (Lucifer Yellow), microdissection and general appearance in the light microscope have shown that the majority of skeletal
fibres isolated from the soleus and extensor digitorum longus (EDL) of adult dystrophic mice (10-14 weeks old) had gross morphological
abnormalities. These abnormalities ranged from simple branching of the fibre to interconnections of many fibre branches which
form a complex syncitium. 3. Segments from fibres of normal appearance and from fibres with morphological deformities were
chemically skinned with Triton X-100 and activated in Ca2(+)- and Sr2(+)-buffered solutions. The different characteristics
of the Ca2(+)- and Sr2(+)-activation curves were also used to identify the fibre type. 4. Gross morphological abnormalities
were observed both in fibres which had predominantly slow-twitch and fast-twitch characteristics. 5. A new group of fibres
was found to exist in the soleus muscle of dystrophic animals and represented about 18% of the entire soleus fibre population.
This group of fibres had predominantly fast-twitch characteristics and some of these fibres were also grossly malformed. 6.
The activation characteristics of individual branches from the same complex syncitium were similar, indicating that the contractile
and regulatory proteins were of one type in one syncitium. 7. Chemically skinned segments from malformed fibres which included
a major deformity between the points of attachment were generally unable to sustain near-maximal forces. 8. The proportion
of malformed fibres which remained intact decreased markedly after prolonged tetanical stimulation of the intact muscle. This
strongly suggests that malformed fibres are also functionally weak and prone to progressive damage when stimulated within
the intact muscle. 9. The presence in large proportions of fibres with gross morphological abnormalities may explain the symptoms
of severe and progressive muscle weakness and muscle loss which are apparent in the 129/ReJ dy/dy mice and possibly even in
the human dystrophies such as Duchenne muscular dystrophy.
1. Investigations were made into the effects of BRL 38227, a potassium channel activator, on ATP-sensitive potassium channels
(K+ATP channels) in single fibres dissociated from the flexor digitorum ...brevis muscle of C57BL/6J mice. 2. In cell-attached
patches BRL 38227 (100 microM) caused activation of a glibenclamide-sensitive potassium current. Linear slope conductance
of the inward current, partial rectification of the outward current and glibenclamide sensitivity indicate that K+ATP channels
are the site of action of BRL 38227. 3. In the absence of ATP at the cytoplasmic side of excised inside-out patches, BRL 38227
caused direct and magnesium-dependent activation of K+ATP channels. The degree of activation diminished with successive applications
of BRL 38227. 4. BRL 38227 also caused activation of K+ATP channels in the presence of low (< 100 microM) but not high (1.0
mM) ATP, particularly in patches containing large numbers of channels. 5. BRL 38227 and 5 microM MgATP failed to activate
channels following complete run-down. 6. Results show that BRL 38227 caused direct activation of K+ATP in skeletal muscle
and that this was mediated through a magnesium-dependent binding site rather than alleviation of inhibition by competitive
displacement of ATP from the inhibitory site.
During the dissolution of the former Carolingian Empire, warfare and plunder went unchecked. An innovative response to this violence was the Church-led initiative known as the Peace of God, perhaps ...history's earliest mass peace movement. In the thirteen essays collected here, leading scholars consider key aspects of the movement and episodes in its history.
We engineered an automated biomechatronics system, MyoRobot, for robust objective and versatile assessment of muscle or polymer materials (bio-)mechanics. It covers multiple levels of muscle ...biosensor assessment, e.g. membrane voltage or contractile apparatus Ca
ion responses (force resolution 1µN, 0-10mN for the given sensor; Ca
range ~ 100nM-25µM). It replaces previously tedious manual protocols to obtain exhaustive information on active/passive biomechanical properties across various morphological tissue levels. Deciphering mechanisms of muscle weakness requires sophisticated force protocols, dissecting contributions from altered Ca
homeostasis, electro-chemical, chemico-mechanical biosensors or visco-elastic components. From whole organ to single fibre levels, experimental demands and hardware requirements increase, limiting biomechanics research potential, as reflected by only few commercial biomechatronics systems that can address resolution, experimental versatility and mostly, automation of force recordings. Our MyoRobot combines optical force transducer technology with high precision 3D actuation (e.g. voice coil, 1µm encoder resolution; stepper motors, 4µm feed motion), and customized control software, enabling modular experimentation packages and automated data pre-analysis. In small bundles and single muscle fibres, we demonstrate automated recordings of (i) caffeine-induced-, (ii) electrical field stimulation (EFS)-induced force, (iii) pCa-force, (iv) slack-tests and (v) passive length-tension curves. The system easily reproduces results from manual systems (two times larger stiffness in slow over fast muscle) and provides novel insights into unloaded shortening velocities (declining with increasing slack lengths). The MyoRobot enables automated complex biomechanics assessment in muscle research. Applications also extend to material sciences, exemplarily shown here for spider silk and collagen biopolymers.
In this study, the membrane potential and cytosolic Ca
2+ were measured in rat myotubes developing in culture from days 6–14. It was found that as the myotubes developed in culture, the resting ...membrane potential (RMP) became more negative during days 6–8, and then did not significantly change until after day 13, when it started to become less negative. The mean RMP measured at days 8–13 was −59 ± 1 mV (
n = 70). The amplitude of action potentials elicited in the myotubes by anode break stimulation increased in size during development (range: 47.5–119 mV) and this closely correlated with the development of a more negative RMP. Cytosolic Ca
2+ was measured in the rat myotubes using the Ca
2+ indicator Fura-2, and no significant change in the resting Ca
2+ was observed during development (days 6–14). Ca
2+ responses triggered by action potentials varied from small slow increases in Ca
2+ that failed to return to the baseline to rapid Ca
2+ transients. The size of the Ca
2+ transients positively correlated with both the observed increase in the RMP during development and the size of the action potential. Larger Ca
2+ transients also had more rapid rates of Ca
2+ decay, indicating a tandem increase in the ability of the sarcoplasmic reticulum to release and resequester Ca
2+ during development of rat myotubes. Repetitive stimulation (10 Hz) of the myotubes exhibiting small Ca
2+ transients produced a step-like rise in Ca
2+. Many myotubes exhibiting larger Ca
2+ transients could not be stimulated at 10 Hz by anode break stimulation due to the presence of action potentials with large hyperpolarisations. However, when these myotubes were depolarised at 10 Hz, they produced a tetanic Ca
2+ response similar to that seen in adult skeletal muscle.
In this study, we applied a method to correct for the altered binding kinetics of Fura-2 for Ca
2+ in vivo, on Ca
2+ fluorescence transients (Ca
2+
F) measured using Fura-2 in single adult fast ...twitch skeletal muscle fibres of the mouse, which exhibit very fast Ca
2+ responses, and rat myotubes developing in culture which exhibit slower Ca
2+ responses (rise time 20–80% of peak of Ca
2+
F transients: 1.81 ± 0.17 ms and 16.14 ± 2.60 ms, respectively). After correction, the Ca
2+ transients (Ca
2+
C) measured in both the adult mouse fibres and the myotubes rose more rapidly (mean rise time of Ca
2+
C transients: adult mouse fibres, 0.76 ± 0.12 ms; rat myotubes, 8.25 ± 2.83 ms) and often exhibited a Ca
2+ spike which exceeded the peak of the Ca
2+
F transient. In the adult mouse fibres, correction increased the mean peak Ca
2+ of the Ca
2+
F transients by a factor of 7 from 0.53 ± 0.08 μM to 3.76 ± 0.71 μM The accuracy of the time course of the corrected Ca
2+ transients was confirmed by comparison to the time course of Ca
2+ transients measured with Mag-Fura-5, which had a similar mean rise time (0.94 ± 0.10 ms,
t-test,
P = 0.80). The more slowly rising Ca
2+ transients measured in the rat myotubes were less affected by the correction process, increasing in mean peak Ca
2+ by a factor of only 1.2 from 0.82 ± 0.17 μM to 0.97 ± 0.15 μM. During the decay phase of the Ca
2+ transients elicited in the adult mouse fibres and the myotubes, the corrected Ca
2+
C signal largely followed the unmodified Ca
2+
F transient. The correction process was found to have little effect on Ca
2+ transients with rise time values greater than 10 ms, which included most of the Ca
2+ transients measured in the myotubes.
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