TEMPERATURE AS MODIFIER OF MAMMALIAN SKELETAL MUSCLE FUNCTION AND OF MUSCLE RESPONSIVENESS TO PHYSIOLOGICAL FACTORS
Funder
National Health and Medical Research Council
Funding Amount
$256,018.00
Summary
Contracting muscles are a major source of heat production in the body. Heat produced by contracting muscles can cause muscle damage if muscle temperature increases above 44oC. Also, overheating from external sources can cause an increase in muscle temperature in the upper physiological range of temperature (37-44oC) which can so readily happen to humans and animals caught in blistering sun or in closed cars parked in the sun. However, very little is known about what happens to the ability of the ....Contracting muscles are a major source of heat production in the body. Heat produced by contracting muscles can cause muscle damage if muscle temperature increases above 44oC. Also, overheating from external sources can cause an increase in muscle temperature in the upper physiological range of temperature (37-44oC) which can so readily happen to humans and animals caught in blistering sun or in closed cars parked in the sun. However, very little is known about what happens to the ability of the skeletal muscle to contract when the temperature increases in this upper physiological range of temperature. This project seeks to fill in this important gap in our knowledge and increase our understanding about the existence of protective mechanisms in muscle to prevent heat-induced damage to the muscle. Such mechanisms would allow the body to operate very close to the lethal range of temperature and may be mainly responsible for the severe muscle weakness in overheated individuals. Results obtained from the project can have far reaching implications for human physiology in general and muscle and exercise physiology in particular and for developing new strategies in the treatment of collapse from body overheating. The project will also produce new knowledge regarding the mechanism of action of drugs used in the treatment of certain mental disorders but which can trigger, in susceptible individuals, uncontrolled contraction of muscles and overheating.Read moreRead less
Molecular Basis Of Ca2+-dependent Disruption Of EC-coupling And Weakness In Skeletal Muscle
Funder
National Health and Medical Research Council
Funding Amount
$530,976.00
Summary
One major cause of weakness in skeletal muscle appears to stem from damage to the mechanism controlling release of calcium ions from internal stores and consequent contraction. This project examines whether the damage is due to excessive levels of intracellular calcium ions activating enzymes that cut a particular vital molecule controlling calcium release. The findings could identify a major factor in muscle weakness in muscular dystrophy and other conditions and lead to specific therapies.
A NEW LOOK AT THE ROLE(S) OF GLYCOGEN AND SUGAR PHOSPHATES IN SKELETAL MUSCLE CONTRACTILITY
Funder
National Health and Medical Research Council
Funding Amount
$193,224.00
Summary
According to textbooks, glycogen in skeletal muscle is a homogenous molecular species whose sole role in muscle contraction is that of a carbohydrate-energy store. Likewise, sugar phosphates, such as glucose1-phosphate (G1-P), glucose 6-phosphate (G6-P), fructose 6-phosphate (F6-P) and fructose 1,6-bisphosphate (F1,6-bP) are generally presented as negatively charged compounds that act only as substrates-products of intermediary reactions in sugar degradation pathways. However, there is now compe ....According to textbooks, glycogen in skeletal muscle is a homogenous molecular species whose sole role in muscle contraction is that of a carbohydrate-energy store. Likewise, sugar phosphates, such as glucose1-phosphate (G1-P), glucose 6-phosphate (G6-P), fructose 6-phosphate (F6-P) and fructose 1,6-bisphosphate (F1,6-bP) are generally presented as negatively charged compounds that act only as substrates-products of intermediary reactions in sugar degradation pathways. However, there is now compelling evidence that (i) glycogen depletion impairs muscle contractility even when there is no shortage of cellular energy, (ii) there are two molecular forms of glycogen, and (iii) sugar phosphates can act as potent modifiers of functional domains in muscle proteins. This project addresses a number of novel questions regarding the role (s) of glycogen and sugar phosphates in muscle contractility and the cellular mechanisms involved. The knowledge produced will further our understanding of the correlation between Excitation-Contraction coupling and different intracellular glycogen pools, and of the molecular basis of prolonged effects of sugar phosphates on the contractile machinery. Furthermore, this work should also generate valuable insights into complex physiological (e.g. fatigue and aging) and pathological (e.g. atherosclerosis, metabolic myopathies) conditions which are still poorly understood.Read moreRead less
Role Of Nitric Oxide And Reactive Oxygen Species In Excitation-contraction Coupling In Skeletal Muscle.
Funder
National Health and Medical Research Council
Funding Amount
$163,250.00
Summary
Excitation-contraction (E-C) coupling is a term used to broadly describe the sequence of cellular events that starts with an electrical signal at the surface membrane of a muscle cell and which then ultimately leads to muscle contraction. Although the overall sequence is known, there remain many gaps in our understanding of the mechanisms involved not only related to normal muscle function but to how this function may be impaired by excessive exercise and disease. Many cellular metabolites contr ....Excitation-contraction (E-C) coupling is a term used to broadly describe the sequence of cellular events that starts with an electrical signal at the surface membrane of a muscle cell and which then ultimately leads to muscle contraction. Although the overall sequence is known, there remain many gaps in our understanding of the mechanisms involved not only related to normal muscle function but to how this function may be impaired by excessive exercise and disease. Many cellular metabolites contribute towards the normal control of muscle contraction, while others contribute to its impairment. Reactive oxygen species (ROS), which includes nitric oxide (NO) and related molecules, are metabolic factors often referred to as cellular oxidants. They are thought to have an essential role in controlling normal muscle function. Paradoxically, they are also implicated in the impairment of muscle function associated with fatigue, disease and aging. How these molecules both control normal muscle activity and also contribute to impairment of such function remains unclear. Thus, the central aim of this project is to identify the mechanisms by which the cellular oxidants, NO and other ROS, both control normal E-C coupling in skeletal muscle fibres and how they contribute to muscle fatigue. Clearly, understanding how skeletal muscle normally contracts is essential in order to better understand how muscle function can become impaired with exercise, disease and age. The work from this study will provide insight into both normal muscle physiology and how muscles fatigue and ultimately provide new methodologies and drugs that may combat fatigue, disease and age related changes to muscle function.Read moreRead less
Regulation Of Extraocular Myosins In Craniofacial Muscles
Funder
National Health and Medical Research Council
Funding Amount
$196,018.00
Summary
Muscles which move the eyeball are highly complex and contain a special motor protein which enables them to contract with the highest speed of all muscles in the body. This protein is found also in muscles of the throat which open and close the airway during coughing, sneezing and swallowing. These muscles also make many other types of motor proteins, giving them a wide spectrum of properties. The functional advantage of having very fast muscles to move the eyes, and protect the airway by preven ....Muscles which move the eyeball are highly complex and contain a special motor protein which enables them to contract with the highest speed of all muscles in the body. This protein is found also in muscles of the throat which open and close the airway during coughing, sneezing and swallowing. These muscles also make many other types of motor proteins, giving them a wide spectrum of properties. The functional advantage of having very fast muscles to move the eyes, and protect the airway by preventing foreign bodies from entering the lungs, is obvious, but how the synthesis of this motor protein is restricted to these muscles is intriguing. Studies in limb muscles have established the principle that the type of motor protein in a muscle is determined by both the type of muscle cells and the type of innervation. Nerves can change the motor proteins in response to the pattern of use imposed by the brain via electrical impulses along its nerve supply. It is known that frequency of nerve impulses to eye muscles are exceptionally high. This project will use several approaches to test the hypothesis that the nerve impulse pattern delivered to these special muscles is involved in the regulation of this motor protein. In one approach, these muscles in rat will be subject to long-term paralysis by cutting their nerve or by the use of botulinum toxin to see if the motor protein is abolished or reduced. In another, the nerve to throat muscles which make this protein will be redirected to another throat muscle which does not normally make this motor protein. These experiments are expected to support the notion that eye and throat muscles are different from all other muscles in the body, and that the normal neural activity from nerves innervating these special muscles is necessary for inducing the synthesis of their motor proteins. These results will greatly help us understand how eye and throat muscles acquire their unique characteristics.Read moreRead less
DHPR ? Subunit Binding To A Variably Spliced Region Of RyR1: A Role In EC Coupling And Myotonic Dystrophy
Funder
National Health and Medical Research Council
Funding Amount
$555,892.00
Summary
We have uncovered a communication pathway between two ion channel molecules in muscle cells that underlies human movement. The pathway is critical in normal mobility and is disrupted in myotonic dystrophy. We will study the molecular components of this pathway to understand normal body function and abnormal function in mytotonic dystrophy. The work will facilitate the design of drugs to relieve the mytotonic dystrophy myopathy and form new and much needed class of specific muscle relaxants.