Biomaterial Database

Postnatal growth of motor nerve terminals in muscles of the mouse. 1985

W G Hopkins, and M C Brown, and R J Keynes

A reduced silver stain was used to examine the development of complexity of motor nerve terminals in the postnatal period. Terminals in three histochemically different muscles were examined in mice aged 12 days to 3 years. The total number and total length of intraterminal axon branches increases with age, but only until animals are 3 months old. Terminals become longest and most branched in the histochemically glycolytic tensor fascia latae (TFL) muscle, shortest and least branched in the oxidative diaphragm, and intermediate in the histochemically mixed gluteus muscle. In addition, myelinated terminal branches develop in TFL and to a lesser extent in the gluteus between 1 and 3 months of age. These myelinated branches appear to be produced by nodal sprouting from the penultimate node of Ranvier of the terminal axon, and also by myelination of pre-existing terminal branches. The diameter of muscle fibres also increases until animals are 3 months old, and there is a good correlation between mean fibre diameter and either mean terminal length or mean number of terminal branches when all muscles at all ages are compared. This suggests that terminal growth could be determined by muscle fibre growth; however, within any given muscle there is little or no correlation between the diameter of a muscle fibre and either the length or number of branches of its nerve terminal, suggesting that terminal morphology is not controlled solely by muscle fibre growth. The presence of a myelinated branch in a nerve terminal is also unrelated to fibre diameter within a given muscle, but again when means are compared there are good, but significantly different correlations for the three different muscles. Thus some kind of muscle or nerve type-specific property additional to a general effect of muscle fibre size influences the development of myelinated terminal branches. Between 3 and 12 months of age terminal complexity remains constant or may decrease slightly. At 19 months or older, when mice are becoming senile, a large proportion of synapses have terminal sprouts and muscle fibres become innervated by two or more distinct axons. These changes can be attributed to the death of some motor neurons and sprouting of the remaining axons.

UI	MeSH Term	Description	Entries
D008815	Mice, Inbred Strains	Genetically identical individuals developed from brother and sister matings which have been carried out for twenty or more generations, or by parent x offspring matings carried out with certain restrictions. All animals within an inbred strain trace back to a common ancestor in the twentieth generation.	Inbred Mouse Strains,Inbred Strain of Mice,Inbred Strain of Mouse,Inbred Strains of Mice,Mouse, Inbred Strain,Inbred Mouse Strain,Mouse Inbred Strain,Mouse Inbred Strains,Mouse Strain, Inbred,Mouse Strains, Inbred,Strain, Inbred Mouse,Strains, Inbred Mouse
D009045	Motor Endplate	The specialized postsynaptic region of a muscle cell. The motor endplate is immediately across the synaptic cleft from the presynaptic axon terminal. Among its anatomical specializations are junctional folds which harbor a high density of cholinergic receptors.	Motor End-Plate,End-Plate, Motor,End-Plates, Motor,Endplate, Motor,Endplates, Motor,Motor End Plate,Motor End-Plates,Motor Endplates
D009046	Motor Neurons	Neurons which activate MUSCLE CELLS.	Neurons, Motor,Alpha Motorneurons,Motoneurons,Motor Neurons, Alpha,Neurons, Alpha Motor,Alpha Motor Neuron,Alpha Motor Neurons,Alpha Motorneuron,Motoneuron,Motor Neuron,Motor Neuron, Alpha,Motorneuron, Alpha,Motorneurons, Alpha,Neuron, Alpha Motor,Neuron, Motor
D009132	Muscles	Contractile tissue that produces movement in animals.	Muscle Tissue,Muscle,Muscle Tissues,Tissue, Muscle,Tissues, Muscle
D009413	Nerve Fibers, Myelinated	A class of nerve fibers as defined by their structure, specifically the nerve sheath arrangement. The AXONS of the myelinated nerve fibers are completely encased in a MYELIN SHEATH. They are fibers of relatively large and varied diameters. Their NEURAL CONDUCTION rates are faster than those of the unmyelinated nerve fibers (NERVE FIBERS, UNMYELINATED). Myelinated nerve fibers are present in somatic and autonomic nerves.	A Fibers,B Fibers,Fiber, Myelinated Nerve,Fibers, Myelinated Nerve,Myelinated Nerve Fiber,Myelinated Nerve Fibers,Nerve Fiber, Myelinated
D009469	Neuromuscular Junction	The synapse between a neuron and a muscle.	Myoneural Junction,Nerve-Muscle Preparation,Junction, Myoneural,Junction, Neuromuscular,Junctions, Myoneural,Junctions, Neuromuscular,Myoneural Junctions,Nerve Muscle Preparation,Nerve-Muscle Preparations,Neuromuscular Junctions,Preparation, Nerve-Muscle,Preparations, Nerve-Muscle
D005260	Female		Females
D000375	Aging	The gradual irreversible changes in structure and function of an organism that occur as a result of the passage of time.	Senescence,Aging, Biological,Biological Aging
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D001369	Axons	Nerve fibers that are capable of rapidly conducting impulses away from the neuron cell body.	Axon