scholarly journals Physiological Signs of the Activation of Bag2 and Chain Intrafusal Muscle Fibers of Gastrocnemius Muscle Spindles in the Cat

1998 ◽  
Vol 80 (1) ◽  
pp. 130-142 ◽  
Author(s):  
A. Taylor ◽  
P. H. Ellaway ◽  
R. Durbaba
Keyword(s):  
Gastrocnemius Muscle ◽  
Muscle Fibers ◽  
Muscle Spindles ◽  
Fiber Types ◽  
Dominant Type ◽  
Intrafusal Muscle ◽  
Chance Distribution ◽  
Intrafusal Fibers ◽  
Intrafusal Muscle Fibers ◽  
Prolonged Response

Taylor, A., P. H. Ellaway, and R. Durbaba. Physiological signs of the activation of bag2 and chain intrafusal muscle fibers of gastrocnemius muscle spindles in the cat. J. Neurophysiol. 80: 130–142, 1998. A method is described for identifying the effect of single gamma static (γs) axons on bag2 or chain intrafusal fibers using random (Poisson-distributed) stimuli. The cross-correlogram of the stimuli with the firing of spindle primary afferents took one of three forms. A large, simple, brief response was taken to indicate pure chain fiber activation and a small, prolonged response to indicate pure bag2 activation. A compound response with brief and prolonged components was taken to be a sign of mixed innervation. The correlogram components could be well fitted with lognormal curves. They could also be transformed into curves of gain as a function of frequency, which were convenient for estimating the strength of the effects. In 68 effects of γs axons on Ia afferents, 16 were pure chain, 17 pure bag2, and 35 mixed. This distribution was significantly different ( P < 0.05) from that expected from chance nonspecific innervation of chain and bag2 fibers. Making use of the estimates of the strength of chain and bag2 effects derived from the gain curves, the classification was modified by treating mixed responses that had one effect more than five times stronger than the other as belonging to the dominant type. The distribution was then as follows: chain 16, bag2 28, and mixed 24. This differed very significantly from the prediction of chance distribution ( P < 0.001). This evidence for some degree of specific innervation of chain and bag2 fibers is discussed in relation to previous work and with regard to the ways in which the two fiber types might be used in natural movements.

scholarly journals The role of muscle spindles in the development of the monosynaptic stretch reflex

2012 ◽  
Vol 108 (1) ◽  
pp. 83-90 ◽  
Author(s):  
Zhi Wang ◽  
LingYing Li ◽  
Eric Frank
Keyword(s):  
Muscle Fibers ◽  
Muscle Spindles ◽  
Synaptic Connections ◽  
Intrafusal Muscle ◽  
Intrafusal Fibers ◽  
Sensory Axons ◽  
Neurotrophin 3 ◽  
Erbb2 Receptor ◽  
Intrafusal Muscle Fibers

Muscle sensory axons induce the development of specialized intrafusal muscle fibers in muscle spindles during development, but the role that the intrafusal fibers may play in the development of the central projections of these Ia sensory axons is unclear. In the present study, we assessed the influence of intrafusal fibers in muscle spindles on the formation of monosynaptic connections between Ia (muscle spindle) sensory axons and motoneurons (MNs) using two transgenic strains of mice. Deletion of the ErbB2 receptor from developing myotubes disrupts the formation of intrafusal muscle fibers and causes a nearly complete absence of functional synaptic connections between Ia axons and MNs. Monosynaptic connectivity can be fully restored by postnatal administration of neurotrophin-3 (NT-3), and the synaptic connections in NT-3-treated mice are as specific as in wild-type mice. Deletion of the Egr3 transcription factor also impairs the development of intrafusal muscle fibers and disrupts synaptic connectivity between Ia axons and MNs. Postnatal injections of NT-3 restore the normal strengths and specificity of Ia–motoneuronal connections in these mice as well. Severe deficits in intrafusal fiber development, therefore, do not disrupt the establishment of normal, selective patterns of connections between Ia axons and MNs, although these connections require the presence of NT-3, normally supplied by intrafusal fibers, to be functional.

scholarly journals FINE STRUCTURE OF RAT INTRAFUSAL MUSCLE FIBERS

1971 ◽  
Vol 51 (1) ◽  
pp. 83-103 ◽  
Author(s):  
William K. Ovalle
Keyword(s):  
Muscle Fiber ◽  
Muscle Fibers ◽  
Muscle Spindles ◽  
Intrafusal Muscle ◽  
Dense Granules ◽  
Intrafusal Muscle Fibers ◽  
Sarcotubular System ◽  
Nuclear Chain ◽  
T System ◽  
Nuclear Bag

An ultrastructural comparison of the two types of intrafusal muscle fibers in muscle spindles of the rat was undertaken. Discrete myofibrils with abundant interfibrillar sarcoplasm and organelles characterize the nuclear chain muscle fiber, while a continuous myofibril-like bundle with sparse interfibrillar sarcoplasm distinguishes the nuclear bag muscle fiber. Nuclear chain fibers possess well-defined and typical M bands in the center of each sarcomere, while nuclear bag fibers contain ill-defined M bands composed of two parallel thin densities in the center of the pseudo-H zone of each sarcomere. Mitochondria of nuclear chain fibers are larger and more numerous than they are in nuclear bag fibers. Mitochondria of chain fibers, in addition, often contain conspicuous dense granules, and they are frequently intimately related to elements of the sarcoplasmic reticulum (SR). Striking differences are noted in the organization and degree of development of the sarcotubular system. Nuclear bag fibers contain a poorly developed SR and T system with only occasional junctional couplings (dyads and triads). Nuclear chain fibers, in contrast, possess an unusually well-developed SR and T system and a variety of multiple junctional couplings (dyads, triads, quatrads, pentads, septads). Greatly dilated SR cisternae are common features of nuclear chain fibers, often forming intimate associations with T tubules, mitochondria, and the sarcolemma. Such dilatations of the SR were not encountered in nuclear bag fibers. The functional significance of these structural findings is discussed.

Histochemical Identification of Three Types of Intrafusal Muscle Fibers in the Cat and Monkey Based on the Myosin ATPase Reaction

1972 ◽  
Vol 50 (3) ◽  
pp. 195-202 ◽  
Author(s):  
W. K. Ovalle ◽  
R. S. Smith
Keyword(s):  
Frozen Section ◽  
Muscle Fibers ◽  
Muscle Spindles ◽  
Myosin Atpase ◽  
Stable Form ◽  
Intrafusal Muscle ◽  
Atpase Reaction ◽  
Intrafusal Muscle Fibers ◽  
Alkaline Conditions ◽  
Acid Stable

Serial frozen section of muscle spindles in the lumbrical muscles of the cat and the monkey were tested with a recently described modification of the myosin ATPase reaction (Guth and Samaha 1970. Exp. Neurol 28, 365). This reaction is able to detect acid-stable, alkaline-labile myosin ATPase and acid-labile, alkaline-stable myosin ATPase. The reactions were carried out by preincubation of the sections at pH 10.4 or 4.35 with incubation in a substrate at pH 9.4. In both the cat and the monkey three types of intrafusal muscle fibers could be detected on the basis of their reaction for myosin ATPase. Nuclear bag fibers could be divided into two types: those containing the acid-stable form of myosin ATPase only, and those containing ATPase detectable under both acid and alkaline conditions. Nuclear chain fibers contained the alkaline-stable form of ATPase only.

Intrafusal muscle fibers of duck muscle spindles

1987 ◽  
Vol 191 (3) ◽  
pp. 225-232 ◽  
Author(s):  
M. N. Adal ◽  
S. B. Chew Cheng
Keyword(s):  
Muscle Fibers ◽  
Muscle Spindles ◽  
Intrafusal Muscle ◽  
Intrafusal Muscle Fibers

scholarly journals Histochemistry of rat intrafusal muscle fibers and their motor innervation.

1978 ◽  
Vol 26 (11) ◽  
pp. 973-988 ◽  
Author(s):  
J Kucera ◽  
K Dorovini-Zis ◽  
W K Engel
Keyword(s):  
Regional Differences ◽  
Motor Nerve ◽  
Muscle Fibers ◽  
Muscle Spindles ◽  
Sensory Innervation ◽  
Staining Reaction ◽  
Intrafusal Muscle ◽  
Intrafusal Muscle Fibers ◽  
Atpase Staining ◽  
Nuclear Bag

Muscle spindles were followed in serial transverse sections of freshly frozen rat soleus muscles. Adenosine triphosphatase (ATPase) histochemical staining reaction was used to identify nuclear bag1, nuclear bag2 and nuclear chain intrafusal muscle fibers. Regional differences in ATPase staining occurred along bag1 and bag2 fibers but not along chain fibers. Bag1 fibers displayed ultrastructural heterogenity when their intra- and extracapsular regions were compared. Simple "diffuse" and more elaborate "plate" motor nerve terminals were demonstrated histochemically along the poles of bag1 and bag2 fibers by staining for cholinesterase. One motor terminal of the "plate" appearance was present on a chain fiber pole. There was no consistent spatial correlation between the intensity of regional ATPase staining along the nuclear bag fibers and the location, number and type of motor endings. Other factors, such as intrafusal fiber sensory innervation and regional differences in active and passive functional recruitment of nuclear bag fibers during muscle activity, may contribute to the ATPase staining variability along the intrafusal fibers.

scholarly journals A HISTOCHEMICAL INVESTIGATION OF INTRAFUSAL FIBERS IN TORTOISE MUSCLE SPINDLES

1972 ◽  
Vol 20 (3) ◽  
pp. 200-204 ◽  
Author(s):  
ALAN CROWE ◽  
ABDUL H.M.F. RAGAB
Keyword(s):  
Propylene Glycol ◽  
Muscle Spindle ◽  
Succinic Dehydrogenase ◽  
Muscle Spindles ◽  
Histochemical Investigation ◽  
Intrafusal Muscle ◽  
Intrafusal Fibers ◽  
Intrafusal Muscle Fibers ◽  
Extensor Digitorum Brevis ◽  
Intrafusal Muscle Fiber

Histochemical investigations upon intrafusal muscle fibers of spindles in the extensor digitorum brevis 1 muscle of the tortoise have been carried out. The localization of phosphorylase, succinic dehydrogenase and adenosine activities together with the demonstration of lipids by the propylene glycol-Sudan method all failed to produce results which could be used to categorize the intrafusal fibers into more than one type. From these results and from previous histologic investigations it is suggested that the tortoise muscle spindle contains just one kind of intrafusal muscle fiber.

scholarly journals Expression of type-specific MHC isoforms in rat intrafusal muscle fibers.

1992 ◽  
Vol 40 (2) ◽  
pp. 293-307 ◽  
Author(s):  
J Kucera ◽  
J M Walro ◽  
L Gorza
Keyword(s):  
Muscle Fibers ◽  
Fiber Types ◽  
Hindlimb Muscles ◽  
Intrafusal Fibers ◽  
Intrafusal Muscle Fibers ◽  
Intrafusal Fiber Types ◽  
Fast Twitch ◽  
Developing Muscle

Myosin heavy chain (MHC) expression by intrafusal fibers was studied by immunocytochemistry to determine how closely it parallels MHC expression by extrafusal fibers in the soleus and tibialis anterior muscles of the rat. Among the MHC isoforms expressed in extrafusal fibers, only the slow-twitch MHC of Type 1 extrafusal fibers was expressed along much of the fibers. Monoclonal antibodies (MAb) specific for this MHC bound to the entire length of bag2 fibers and the extracapsular region of bag1 fibers. The fast-twitch MHC isoform strongly expressed by bag2 and chain fibers had an epitope not recognized by MAb to the MHC isoforms characteristic of developing muscle fibers or the three subtypes (2A, 2B, 2X) of Type 2 extrafusal fibers. Therefore, intrafusal fibers may express a fast-twitch MHC that is not expressed by extrafusal fibers. Unlike extrafusal fibers, all three intrafusal fiber types bound MAb generated against mammalian heart and chicken limb muscles. The similarity of the fast-twitch MHC of bag2 and chain fibers and the slow-tonic MHC of bag1 and bag2 fibers to the MHC isoforms expressed in avian extrafusal fibers suggests that phylogenetically primitive MHCs might persist in intrafusal fibers. Data are discussed relative to the origin and regional regulation of MHC isoforms in intrafusal and extrafusal fibers of rat hindlimb muscles.

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