Close appositions and junctions of plasma membranes of intrafusal fibres in mammalian muscle spindles

1967 ◽  
Vol 296 (4) ◽  
pp. 337-345 ◽  
Author(s):  
N. Corvaja ◽  
V. Marinozzi ◽  
O. Pompeiano
Keyword(s):  
Plasma Membranes ◽  
Muscle Spindles ◽  
Mammalian Muscle ◽  
Intrafusal Fibres

scholarly journals The Fine Structure of Muscle Spindles in the Lumbrical Muscles of the Rat

1960 ◽  
Vol 7 (4) ◽  
pp. 725-742 ◽  
Author(s):  
Neil C. R. Merrillees
Keyword(s):  
Plasma Membranes ◽  
Sensory Nerve ◽  
Solid Material ◽  
Peripheral Zone ◽  
Muscle Spindles ◽  
Polar Regions ◽  
Golgi Bodies ◽  
Intrafusal Fibres ◽  
Motor End Plates ◽  
Lumbrical Muscles

Lumbrical muscles of young rats were fixed with OsO4 and embedded in methacrylate for electron microscopy. The spindle capsule was found to be continuous with and similar in structure to the sheath of Henle surrounding the nerves supplying the spindle. The capsule consists of several closely applied concentric cytoplasmic sheets. Each sheet is about 1,000 A thick and has no fenestrations. Many caveolae and vesicles in the cytoplasm suggest active transport through the sheets. The periaxial space fluid contains much solid material. It is suggested that the capsule and periaxial space regulate internal chemical environment. The interfibrillar structures are less evident in the polar regions of intrafusal fibres than in extrafusal fibres. Simple motor end-plates occur on the polar regions of intrafusal fibres. In the myotube region of the intrafusal fibre a peripheral zone of myofibrils surrounds a cytoplasmic core containing nuclei, mitochondria, Golgi bodies, reticulum, and a few lipid-like granules. Naked sensory endings lie on the myotube "in parallel" with the underlying myofilaments. Naked processes of the primary sensory ending deeply indent the muscle plasma membrane and the underlying wisps of myofilament in the nuclear bag region. The plasma membranes of sensory nerve ending and intrafusal muscle fibre are about 200 A apart.

The differentiation of two types of intrafusal fibres in rabbit muscle spindles

1970 ◽  
Vol 317 (3) ◽  
pp. 187-197 ◽  
Author(s):  
N. Corvaja ◽  
O. Pompeiano
Keyword(s):  
Muscle Spindles ◽  
Rabbit Muscle ◽  
Intrafusal Fibres

The Early Development of Muscle Spindles in the Rat

1973 ◽  
Vol 12 (1) ◽  
pp. 175-195
Author(s):  
ALICE MILBURN
Keyword(s):  
Close Association ◽  
Large Diameter ◽  
Muscle Spindles ◽  
Muscle Fibres ◽  
Intrafusal Muscle ◽  
Intrafusal Fibres ◽  
Fusimotor Innervation ◽  
Nuclear Chain ◽  
Intramuscular Nerve

The morphogenesis of muscle spindles in rat lower hind-limb muscles has been investigated using the electron microscope. The earliest detectable spindles are seen in the 19.5-day foetus and consist of a single myotube bearing simple nerve terminals of the large primary afferent axon from nearby unmyelinated intramuscular nerve trunks. The capsule forms by an extension of the perineural epithelium of the supplying nerve fasciculus, and is confined initially to the innervated zone. Myonuclei accumulate in this region, so that the first intrafusal muscle fibre to develop is a nuclear-bag fibre. Myoblasts, present within the capsule of the spindle throughout its development, fuse to form a smaller less-differentiated myotube by the 20-day foetal stage. This new myotube matures by close association with the initial fibre, and by birth (21-22 days gestation) has formed the smaller, intermediate bag fibre, that has been identified histochemically and ultrastructurally in the adult. The nuclear-chain fibres develop in the same way; myoblasts fuse to form satellite myotubes that mature in pseudopodial apposition to one of the other fibres within its basement membrane. This apposition consists of extensions of sarcoplasm from the developing myotube into the supporting fibre. By the 4-day postnatal stage the full adult complement of 4 intrafusal muscle fibres is present, although ultrastructural variations, seen in the adult, are not differentiated. The fusimotor innervation begins to arrive at birth, but is not mature until the 12th postnatal day, when the myofibrillar ultrastructural differentiation, including the loss of the M-line in the large-diameter bag fibre, is complete. The periaxial space appears at the same time. It is suggested that the sequential development of the intrafusal fibres is a reflexion of the decreasing morphogenetic effect of the afferent innervation, whereas the role of the fusimotor innervation is in ultrastructural, myofibrillar differentiation.

Responses of primary and secondary endings of isolated mammalian muscle spindles to sinusoidal length changes

1977 ◽  
Vol 40 (5) ◽  
pp. 1113-1120 ◽  
Author(s):  
C. C. Hunt ◽  
D. Ottoson
Keyword(s):  
Impulse Activity ◽  
Receptor Potential ◽  
Muscle Spindles ◽  
Fixed Frequency ◽  
Potential Response ◽  
Mammalian Muscle ◽  
Spindle Poles ◽  
Highly Nonlinear ◽  
Before And After ◽  
Length Changes

1. Responses of primary and secondary endings of isolated cat spindles to sinusoidal length changes have been recorded before and after block of impulse activity by tetrodotoxin. 2. Primary endings may discharge with each cycle of sinusoidal stretch at 25-50 Hz, with stretch amplitudes applied to the spindle poles as small as 1 micron. Thresholds are higher at lower frequencies. 3. In primary endings, amplitude of the receptor potential varies with frequency and magnitude of sinusoidal stretch. At a given stretch amplitude, the receptor-potential response increases markedly between 1 and 10 Hz. At a fixed frequency, for example, at Hz, the response to graded amplitude of sinusoidal stretch is highly nonlinear, sensitivity decreasing with large amplitudes. 4. Secondary endings show a much higher threshold than primary endings to sinusoidal stretch. Thus, at 25 Hz, secondary endings required stretch amplitudes of 50-100 micron to evoke discharge. Relatively large amplitudes of stretch were also required to evoked detectable receptor potentials. Over the range studied, the receptor potential varied more linearly with stretch amplitude in secondary than in primary endings.

Localization of normal and reinnervated mammalian muscle spindles for microscopy

1972 ◽  
Vol 39 (1) ◽  
pp. 240-244 ◽  
Author(s):  
Mark De Santis ◽  
William O. Whetsell ◽  
Karen Francis
Keyword(s):  
Muscle Spindles ◽  
Mammalian Muscle

Initial burst of primary endings of isolated mammalian muscle spindles

1976 ◽  
Vol 39 (2) ◽  
pp. 324-330 ◽  
Author(s):  
C. C. Hunt ◽  
D. Ottoson
Keyword(s):  
Direct Evidence ◽  
Receptor Potential ◽  
Muscle Spindles ◽  
Initial Component ◽  
Thin Filaments ◽  
Tension Development ◽  
Initial Burst ◽  
Mammalian Muscle ◽  
Mechanical Factors ◽  
Early Rise

The initial burst has been studied in primary endings of isolated mammalian muscle spindles subject to controlled ramp-and-hold stretch. Near the onset of ramp stretch the primary ending discharges at a frequency dependent on stretch velocity. The initial burst is reduced or abolished by repetitive stretch. After block of impulse activity by tetrodotoxin, the receptor potential of primary endings shows an initial component, a rapid depolarization which occurs near the onset of ramp stretch at the same time as the initial burst. This initial component depends, in rate of rise and amplitude, on stretch velocity. It is also reduced or abolished by repetitive stretch. Recording of tension development by the isolated spindle in response to ramp-and-hold stretch shows an early rise in tension associated with the initial burst and the initial component of the receptor potential. This tension rise is also dependent on stretch velocity and is reduced or abolished by repetitive stretch. The results provide direct evidence that the initial burst results from mechanical factors, probably from cross bridge formation between thick and thin filaments as has been suggested (3).

Re-examination of a linear systems approach to the behavior of mammalian muscle spindles

1983 ◽  
Vol 48 (2) ◽  
pp. 85-90 ◽  
Author(s):  
W. J. Daunicht
Keyword(s):  
Linear Systems ◽  
Systems Approach ◽  
Muscle Spindles ◽  
Mammalian Muscle

Abundance, localization, and insulin-induced translocation of glucose transporters in red and white muscle

1992 ◽  
Vol 263 (2) ◽  
pp. C443-C452 ◽  
Author(s):  
A. Marette ◽  
J. M. Richardson ◽  
T. Ramlal ◽  
T. W. Balon ◽  
M. Vranic ◽  
...  
Keyword(s):  
Muscle Cell ◽  
Plasma Membranes ◽  
White Muscle ◽  
Glucose Transporter ◽  
Glucose Transporters ◽  
Muscle Spindles ◽  
Molar Ratio ◽  
Type I ◽  
Slow Twitch ◽  
Fast Twitch

D-Glucose protectable cytochalasin B (CB) binding to subcellular membrane fractions was used to determine glucose transporter number in red (quadriceps-gastrocnemius-soleus) and white (quadriceps-gastrocnemius) rat muscle. CB binding was twofold higher in isolated plasma membranes of red than of white muscle. In contrast, the number of transporters in an isolated insulin-sensitive intracellular membrane organelle was similar in the two muscle groups. Immunoblotting and immunofluorescence microscopy with anti-GLUT4 and anti-GLUT1 antibodies indicated that both GLUT1 and GLUT4 transporter isoforms account for the higher abundance of CB binding sites in plasma membranes of red than of white muscle. Immunofluorescence localized GLUT4 to both the surface and the interior of the muscle cell and demonstrated that type I (slow twitch oxidative) and type IIa (fast twitch oxidative-glycolytic) fibers are enriched in GLUT4 protein compared with type IIb (fast twitch glycolytic) fibers. In contrast, GLUT1 reactivity was restricted to the surface of the muscle cell and was also highly enriched in the perineurial sheaths of peripheral nerves and the capsules of muscle spindles present in both red and white muscles. Insulin caused a twofold increase in CB binding in isolated plasma membranes of red or white muscles with a corresponding 40-50% decrease in CB binding in isolated intracellular membranes. These changes in CB binding were paralleled by similar changes in the membrane distribution of the GLUT4 glucose transporter isoform and in glucose transport activity measured after insulin perfusion of hindquarter muscles. In contrast, insulin did not change the distribution of either GLUT1 glucose transporters or Na(+)-K(+)-ATPase alpha 1-subunits. The molar ratio of GLUT4 to GLUT1 in red and white muscle plasma membranes was found to be 4:1 in the basal state and 7:1 in the insulin-stimulated state. These results indicate that red muscle contains a higher amount of GLUT1 and GLUT4 transporters at the plasma membrane than white muscle in the basal and insulin-stimulated states but that GLUT4 translocation does not differ between muscle types. In addition, GLUT4 expression correlates with the metabolic nature (oxidative vs. glycolytic) of skeletal muscle fibers, rather than with their contractile properties (slow twitch vs. fast twitch).

Prolonged Changes in the Discharge of Mammalian Muscle Spindles Following Tendon Taps or Muscle Twitches.

1959 ◽  
Vol 46 (2-3) ◽  
pp. 185-193 ◽  
Author(s):  
RAGNAR GRANIT ◽  
SABURO HOMMA ◽  
PETER B. C. MATTHEWS
Keyword(s):  
Muscle Spindles ◽  
Mammalian Muscle

scholarly journals The effect of sympathetic stimulation on mammalian muscle spindles

1960 ◽  
Vol 151 (2) ◽  
pp. 332-341 ◽  
Author(s):  
C. C. Hunt
Keyword(s):  
Muscle Spindles ◽  
Sympathetic Stimulation ◽  
Mammalian Muscle
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