Researchers at the University of Liège, Eric Parmentier and Marc Thiry, have found a distinct plan of muscle fibers in the Mediterranean fish, Parophidion vassali, possibly changing our understanding of muscle contraction. The history of the description of skeletal muscles has its origins in the observations made by the Dutch biologist Antoni van Leeuwenhoek, a precursor of cell biology and microbiology who, in a short article published in 1712 in the Philosophical Transactions of the Royal Society, reported, thanks to the usage of a portable single-lens microscope, the first description of muscle fibers from the whale. Subsequent studies have led to increasingly clear descriptions, consisting of the identification of the different particles that make up the muscle and an explanation of how it works, in particular the model of muscle contraction proposed by the biophysicist Andrew Huxley in 1957. Comparison of the company of “timeless” skeletal muscle with parallel myofibrils and sonic muscle with lattice myofibrils in Parophidion vassali. The fastest muscles are discovered in the sonic muscles of fish, where certain species produce noises using muscles that agreement at a frequency of in between 100 and 300 Hz, i.e. 100 to 300 contraction/relaxation cycles per second.
Longitudinal area highlighting the lattice-like setup within the sonic muscle in Parophidion vassali. Credit: Marc Thiry/University of Liège
Scientists have actually simply made the unexpected discovery of a novel company of muscle fibers in Parophidion vassali, a fish that resides in the Mediterranean Sea and, like many fish, uses specialized muscles to produce sounds. This is a crucial discovery that might well change our understanding of contraction.
Scientists at the University of Liège, Eric Parmentier and Marc Thiry, have actually found an unique plan of muscle fibers in the Mediterranean fish, Parophidion vassali, possibly changing our understanding of contraction. This distinct network-like setup of myofibrils within the muscle fiber might permit rapid contractions while retaining strength. More research is required to totally comprehend this unique muscle fiber structure and its practical implications.
The history of the description of skeletal muscles has its origins in the observations made by the Dutch biologist Antoni van Leeuwenhoek, a precursor of cell biology and microbiology who, in a post released in 1712 in the Philosophical Transactions of the Royal Society, reported, thanks to the usage of a portable single-lens microscope, the very first description of muscle fibers from the whale. (See About Muscle Fibers at the bottom of this article.).
Subsequent research studies have actually resulted in progressively clear descriptions, consisting of the recognition of the different particles that comprise the muscle and a description of how it works, in particular the model of muscle contraction proposed by the biophysicist Andrew Huxley in 1957. Over the last 300 years, numerous research studies have extended the representation of muscle fiber company to various taxa. This has actually revealed that the basic company of striated muscle fibers has actually stayed perfectly saved in all groups of vertebrate animals studied to date.
Figure 1. Comparison of the organization of “traditional” skeletal muscle with parallel myofibrils and sonic muscle with lattice myofibrils in Parophidion vassali. Credit: E.Parmentier/ M.Thiry/ Université de Liège.
Conversely, fibers low in myofibrils with an abundance of sarcoplasmic reticulum and many mitochondria are present in muscles that develop an increased speed of contraction. The fastest muscles are discovered in the sonic muscles of fish, where particular types produce sounds using muscles that contract at a frequency of in between 100 and 300 Hz, i.e. 100 to 300 contraction/relaxation cycles per second.
A current study brought out in collaboration between the Evolutionary and practical Morphology Laboratory, and the Cell and Tissue Biology Laboratory has actually revealed a brand-new plan of myofibrils within the fibers of a sonic muscle in the fish Parophidion vassali. Instead of being set up in parallel, the myofibrils form an enormous network within the muscle fiber, explains Prof Eric Parmentier, director of the Functional and Evolutionary Morphology Laboratory at the University of Liège.
Each myofibril subdivides into two branches at each sarcomere, one connecting to the myofibril above and the other linking to the myofibril below (Figure 1B). This new muscle fiber style might result in a muscle that contracts quickly while keeping strength. The scarceness of myofibrils and the high volume inhabited by the sarcoplasmic reticulum favor fibers that agreement rapidly.
” The network structure of the myofibrils would allow more myosin heads to form cross-bridges with the actin myofilaments, which would increase strength in this fast muscle,” explains Prof Marc Thiry, Director of the Cell and Tissue Biology Laboratory. “In addition, many mitochondria unusually arranged within the Z striae (very long in these fibers: 700 nm compared to 70 to 150 nm in a standard muscle) appear to supply the energy required to produce lasting sounds.”.
This new type of organization of striated muscle fibers, never before explained in the scientific literature, and which would for that reason make it possible to integrate muscular strength and speed, requires more studies to comprehend how it works and to figure out whether there are adaptations at the level of the various molecules included in these muscles.
Longitudinal section in a classic skeletal muscle. Credit: Marc Thiry/University of Liège.
About Muscle Fibers.
Striated skeletal muscle fibers or cells represent the primary systems of voluntary muscles (muscles that make it possible for motions such as mobility or posture maintenance) in animals. “Each fiber is characterized by numerous contractile components, actin, and myosin myofilaments, arranged in bundles parallel to the muscle fibers long axis, called myofibrils.
In the longitudinal section under the optical microscope, these fibers appear as a succession of light and dark bands located at the very same level for each myofibril, providing the appearance of transverse striation to the muscle fiber. The part of the myofibril in between two Z striae is called a sarcomere and represents the contractile unit of the myofibril.
The myofibrils occupy a large cell volume and are surrounded by cisternae of the smooth endoplasmic reticulum (or sarcoplasmic reticulum), which saves the calcium necessary for muscle contraction. In addition, mitochondria are situated near to the myofibrils; they are the main source of ATP providing energy for contraction.
