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1.
Diversity in expression of myosin heavy chain isoforms and M-band proteins in rat muscle spindles 总被引:1,自引:0,他引:1
The composition of adult rat soleus muscle spindles, with respect to myosin heavy chain isoforms and M-band proteins, was studied by light-microscope immunohistochemistry. Serial sections were labelled with antibodies against slow tonic, slow twitch, fast twitch and neonatal myosin isoforms as well as against myomesin, M-protein and the MM form of creatine kinase. Intrafusal fiber types were distinguished according to the pattern of ATPase activity following acid and alkaline preincubations. Nuclear bag1 fibers were always strongly stained throughout with anti-slow tonic myosin, were positive for anti-slow twitch myosin towards and in the C-region but were unstained with anti-fast twitch and anti-neonatal myosins. The staining of nuclear bag2 fibers was in general highly variable. However, they were most often strongly stained by anti-slow tonic myosin in the A-region and gradually lost this reactivity towards the poles, whereas a positive reaction with anti-slow twitch myosins was found along the whole fiber. Regional staining variability with anti-neonatal and anti-fast myosins was apparent, often with decreasing intensity towards the polar regions. Nuclear chain fibers showed strong transient reactivity with anti-slow tonic myosin in the equatorial region, did not react with anti-slow twitch and were always evenly stained by anti-fast twitch and anti-neonatal myosins. All three intrafusal fiber types were stained with anti-myomesin. Nuclear bag1 fibers lacked staining for M-protein, whereas bag2 fibers displayed intermediate staining, with regional variability, often increasing in reactivity towards the polar regions. Chain fibers were always strongly stained by anti-M-protein. The MM form of creatine kinase was present in all three fiber types, but bag1 fibers were less reactive and clear striations were not observed, in contrast to bag2 and chain fibers. Out of 38 cross sectioned spindles two were found to have an atypical fiber composition (lack of chain fibers) and a rather diverse staining pattern for the different antibodies tested. Taken together, the data show that in adult rat soleus, slow tonic and neonatal myosin heavy chain isoforms are only expressed in the muscle spindle fibers and that each intrafusal fiber type has a unique, although variable, composition of myosin heavy chain isoforms and M-band proteins. We propose that both motor and sensory innervation might be the determining factors regulating the variable expression of myosin heavy chain isoforms and M-band proteins in intrafusal fibers of rat muscle spindles. 相似文献
2.
E Katayama T Wakabayashi F Reinach T Masaki D A Fischman 《Journal of biochemistry》1984,95(3):721-727
MF-18, one of the monoclonal antibodies generated to chicken myosin, cross-reacted with rabbit skeletal myosin subfragment-1 (S1). Utilizing an improved procedure of immuno-blotting, a decrease in reactivity of MF-18 to S1 by trinitrophenylation was observed. This indicates that the reactive lysyl residue is very close to the hapten site. This is consistent with the evidence that the hapten site resides in the 26,000 dalton tryptic fragment of S1. Use of such antibodies as labels may open the way to determining the location of specific hapten sites in the three-dimensional image of actin-S1 complex reconstructed from the electron micrographs. 相似文献
3.
4.
A system has been developed for the in vitro development of chick skeletal muscle monolayers, in which a burst of synchronous fusion occurs, such that some 40% of the spindle-shaped cells fuse in a 10-hr period. Cells inhibited from synthesizing DNA by ara-C do fuse, but at a later time than the normal burst. If ara-C is added to cultures 6 hr or more before the normal fusion time, fusion is delayed, but no delay results when the drug is added after this time. A medium change will delay the fusion if done 4 hr or more before fusion, but gives no delay if done later. Cells grown in conditioned medium fuse some 10 hr earlier than controls, even in the presence of ara-C, as do cultures prepared at higher than normal cell densities. The data suggest that muscle cell fusion is independent of DNA synthesis in vitro, but depends upon a modification of the culture medium to a sufficient degree required for initiating the synthetic program for fusion. 相似文献
5.
AN ELECTRON MICROSCOPE STUDY OF MYOFIBRIL FORMATION IN EMBRYONIC CHICK SKELETAL MUSCLE 总被引:23,自引:21,他引:2
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Donald A. Fischman 《The Journal of cell biology》1967,32(3):557-575
The formation of myofibrils in the developing leg muscle of the 12-day chick embryo was studied by electron microscopy. Myofilaments of two varieties, thick (160–170 A in diameter) and thin (60–70 A in diameter), which have been designated myosin and actin filaments, respectively, on the basis of their similarity to natural and synthetic myosin and actin filaments, appear in the cytoplasm of developing muscle cells. There is a greater than 7:1 ratio of thin to thick filaments in these young myofibers. The free myofilaments become aligned in the long axis of the cells, predominantly in subsarcolemmal locations, and aggregate into hexagonally packed arrays of filaments. The presence of Z band material or M band cross-bridges do not appear to be essential for the formation or spacing of these aggregates of filaments. Formation of the Z band lattices occurs coincidentally with the back-to-back apposition of thin filaments. An hypothesis concerning myofibril growth, based on the self-assembly characteristics of the filaments, is presented. 相似文献
6.
Nickel Substitution for Calcium in Excitation-Contraction Coupling of Skeletal Muscle 总被引:3,自引:1,他引:2
In 1962 Frank (22) reported that the addition of any one of a number of divalent cations, including Ni, to a Ca-free Ringer solution prevented the rapid loss of contractility seen in the absence of external Ca. To investigate further the Ni-Ca substitution, studies were made of 45Ca and 63Ni exchange during contraction and at rest using frog striated muscle. In contrast to 45Ca, it was found that there is no increase of 63Ni uptake associated with a K contracture of the sartorius muscle. The rates of loss of 63Ni and 45Ca from resting toe muscles previously bathed in the respective radioisotopes are not significantly different. Resting and action potentials, after 1 hr in a Ringer solution with Ni replacing Ca, closely resemble these potentials in normal Ca-Ringer's solution. Studies on the syneresis of isolated myofibrils indicate that Ni cannot replace Ca in activating this reaction. It is suggested that Ca is required for at least two steps in E-C coupling: one is the spread of excitation at the sarcolemma and transverse tubular system; the second is the activation of actomyosin ATPase. Conceivably Ni can substitute for Ca in the former but not in the latter. 相似文献
7.
Enzyme-induced Formation of Spheres from Cells and Envelopes of Escherichia coli 总被引:5,自引:5,他引:0
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Normal and filamentous whole cells and isolated envelopes of Escherichia coli B were exposed to various enzymatic treatments to remove surface layers and to characterize the component(s) conferring rigidity in this organism. Modification of cell rigidity was determined by sphere formation in both whole cells and isolated envelopes. Enzymes capable of converting trypsinized normal or untreated filamentous whole cells and untreated envelopes to spheres included: lysozyme plus ethylenediaminetetraacetic acid, clostridial phospholipase C, and phospholipase D from cabbage. These data suggest that there are at least two components essential for maintenance of cell rigidity in E. coli B. The first is the peptidoglycan (mucopeptide), which is susceptible to lysozyme. The second is a phospholipid which is either covalently linked to the mucopeptide or in close association with it. This phospholipase C-sensitive component is protected more completely in normal than in filamentous whole cells by a protein layer which is easily modified by trypsin treatment to allow enzymatically induced sphere formation to occur. 相似文献
8.
Direct sequencing of the mitochondrial displacement loop (D-loop) of shrews
(genus Sorex) for the region between the tRNA(Pro) and the conserved
sequence block-F revealed variable numbers of 79-bp tandem repeats. These
repeats were found in all 19 individuals sequenced, representing three
subspecies and one closely related species of the masked shrew group (Sorex
cinereus cinereus, S. c. miscix, S. c. acadicus, and S. haydeni) and an
outgroup, the pygmy shrew (S. hoyi). Each specimen also possessed an
adjacent 76-bp imperfect copy of the tandem repeats. One individual was
heteroplasmic for length variants consisting of five and seven copies of
the 79-bp tandem repeat. The sequence of the repeats is conducive to the
formation of secondary structure. A termination-associated sequence is
present in each of the repeats and in a unique sequence region 5' to the
tandem array as well. Mean genetic distance between the masked shrew taxa
and the pygmy shrew was calculated separately for the unique sequence
region, one of the tandem repeats, the imperfect repeat, and these three
regions combined. The unique sequence region evolved more rapidly than the
tandem repeats or the imperfect repeat. The small genetic distance between
pairs of tandem repeats within an individual is consistent with a model of
concerted evolution. Repeats are apparently duplicated and lost at a high
rate, which tends to homogenize the tandem array. The rate of D- loop
sequence divergence between the masked and pygmy shrews is estimated to be
15%-20%/Myr, the highest rate observed in D-loops of mammals. Rapid
sequence evolution in shrews may be due either to their high metabolic rate
and short generation time or to the presence of variable numbers of tandem
repeats.
相似文献
9.
10.
大鼠胼胝体内神经肽Y免疫反应阳性纤维的发育 总被引:1,自引:0,他引:1
本实验用免疫组织化学ABC法研究了大鼠胼胝体内神经肽Y免疫反应阳性(NPY-IR)纤维的生后发育。结果发现,许多NPY-IR纤维在大鼠出生时便存在于胼胝体内。NPY-IR胼胝体纤维的密度在生后1周内继续逐渐增高,在第2周内达到最高峰。之后,NPY-IR胼胝体纤维的密度逐渐下降,至第3周末时接近成年时的水平,即仅有少量NPY-IR纤维存在于胼胝体内。这些结果提示在大鼠早期生后发育过程中许多NPY-IR胼胝体纤维是暂时性的,其作用可能与大脑皮质的机能发育有关。 相似文献