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21.
Intermediate filaments in nervous tissues 总被引:29,自引:30,他引:29
Intermediate filaments have been isolated from rabbit intradural spinal nerve roots by the axonal flotation method. This method was modified to avoid exposure of axons to low ionic strength medium. The purified filaments are morphologically 75-80 percent pure. The gel electrophoretogram shows four major bands migrating at 200,000, 145,000, 68,000, and 60,000 daltons, respectively. A similar preparation from rabbit brain shows four major polypeptides with mol wt of 200,000 145,000, 68,000, and 51,000 daltons. These results indicate that the neurofilament is composed of a triplet of polypepetides with mol wt of 200,000, 145,000, and 68,000 daltons. The 51,000-dalton band that appears in brain filament preparations as the major polypeptide seems to be of glial origin. The significance of the 60,000- dalton band in the nerve root filament preparation is unclear at this time. Antibodies raised against two of the triplet proteins isolated from calf brain localize by immunofluorescence to neurons in central and peripheral nerve. On the other hand, an antibody to the 51,000-dalton polypeptide gives only glial staining in the brain, and very weak peripheral nerve staining. Prolonged exposure of axons to low ionic strength medium solubilizes almost all of the triplet polypeptides, leaving behind only the 51,000- dalton component. This would indicate that the neurofilament is soluble at low ionic strength, whereas the glial filament is not. These results indicate that neurofilaments and glial filaments are composed of different polypeptides and have different solubility characteristics. 相似文献
22.
Effects of EDTA treatment upon the protein subunit composition and mechanical properties of mammalian single skeletal muscle fibers 总被引:9,自引:0,他引:9 下载免费PDF全文
Considerable interest has been focused on the role of myosin light chain LC(2) in the contraction of vertebrate striated muscle. A study was undertaken to further our investigations (Moss, R.L., G.G. Giulian, and M.L. Greaser, 1981, J. Biol. Chem., 257:8588-8591) of the effects of LC(2) removal upon contraction in skinned fibers from rabbit psoas muscles. Isometric tension and maximum velocity of shortening, V(max), were measured in fiber segments prior to LC(2) removal. The segments were then bathed at 30 degrees C for up to 240 min in a buffer solution containing 20 mM EDTA in order to extract up to 60 percent of the LC(2). Troponin C (TnC) was also partially removed by this procedure. Mechanical measurements were done following the EDTA extraction and the readditions of first TnC and then LC(2) to the segments. The protein subunit compositions of the same fiber segments were determined following each of these procedures by SDS PAGE of small pieces of the fiber. V(max) was found to decrease as the LC(2) content of the fiber segments was reduced by increasing the duration of extraction. EDTA treatment also resulted in substantial reductions in tension due mainly to the loss of TnC, though smaller reductions due to the extraction of LC(2) were also observed. Reversal of the order of recombination of LC(2) and TnC indicated that the reduction in V(max) following EDTA treatment was a specific effect of LC(2) removal. These results strongly suggest that LC(2) may have roles in determining the kinetics and extent of interaction between myosin and actin. 相似文献
23.
Relationships among msx gene structure and function in zebrafish and other vertebrates 总被引:4,自引:2,他引:4
Ekker M; Akimenko MA; Allende ML; Smith R; Drouin G; Langille RM; Weinberg ES; Westerfield M 《Molecular biology and evolution》1997,14(10):1008-1022
The zebrafish genome contains at least five msx homeobox genes, msxA, msxB,
msxC, msxD, and the newly isolated msxE. Although these genes share
structural features common to all Msx genes, phylogenetic analyses of
protein sequences indicate that the msx genes from zebrafish are not
orthologous to the Msx1 and Msx2 genes of mammals, birds, and amphibians.
The zebrafish msxB and msxC are more closely related to each other and to
the mouse Msx3. Similarly, although the combinatorial expression of the
zebrafish msx genes in the embryonic dorsal neuroectoderm, visceral arches,
fins, and sensory organs suggests functional similarities with the Msx
genes of other vertebrates, differences in the expression patterns preclude
precise assignment of orthological relationships. Distinct duplication
events may have given rise to the msx genes of modern fish and other
vertebrate lineages whereas many aspects of msx gene functions during
embryonic development have been preserved.
相似文献
24.
Popov SG Villasmil R Bernardi J Grene E Cardwell J Wu A Alibek D Bailey C Alibek K 《Biochemical and biophysical research communications》2002,293(1):349-355
Lethal toxin is a major anthrax virulence factor, causing the rapid death of experimental animals. Lethal toxin can enter most cell types, but only certain macrophages and cell lines are susceptible to toxin-mediated cytolysis. We have shown that in murine RAW 264.7 cells, sublytic amounts of lethal toxin trigger intracellular signaling events typical for apoptosis, including changes in membrane permeability, loss of mitochondrial membrane potential, and DNA fragmentation. The cells were protected from the toxin by specific inhibitors of caspase-1, -2, -3, -4, -6, and -8. Phagocytic activity of macrophages was inhibited by sublytic concentrations of lethal toxin. Infection of cells with anthrax (Sterne) spores impaired their bactericidal capacity, which could be reversed by a lethal toxin inhibitor, bestatin. We suggest that apoptosis rather than direct lysis is biologically relevant to lethal toxin intracellular activity. 相似文献
25.
Nitric oxide (NO) has been reported to act both as a destructive and a protective agent in the pathogenesis of the injuries
that occur during hypoxia/reoxygenation (H/R). It has been suggested that this dual role of NO depends directly on the isoform
of NO synthase (NOS) involved. In this work, we investigate the role that NO derived from endothelial NOS (eNOS) plays in
cardiac H/R-induced injury. Wistar rats were submitted to H/R (hypoxia for 30 min; reoxygenation of 0 h, 12 h and 5 days),
with or without prior treatment using the selective eNOS inhibitor l-NIO (20 mg/kg). Lipid peroxidation, apoptosis and protein nitration, as well as NO production (NOx), were analysed. The results
showed that l-NIO administration lowered NOx levels in all the experimental groups. However, no change was found in the lipid peroxidation
level, the percentage of apoptotic cells or nitrated protein expression, implying that eNOS-derived NO may not be involved
in the injuries occurring during H/R in the heart. We conclude that l-NIO would not be useful in alleviating the adverse effects of cardiac H/R. 相似文献
26.
Molecular population genetics of ref(2)P, a locus which confers viral resistance in Drosophila 总被引:4,自引:0,他引:4
The ref(2)P locus (2-54.2) is polymorphic for two allelic forms in natural
populations of Drosophila melanogaster, ref(2)Po and ref(2)Pp. The latter
allele confers resistance to the rhabdovirus sigma infecting wild
populations. Previous work, based on a small sample of prescreened
restrictive (resistant) and permissive (susceptible) alleles, identified a
large number of amino acid replacement changes (7) relative to synonymous
changes (1). Such protein variability could be the result of
variation-enhancing selection. To further test the selection hypothesis, we
have examined the DNA sequences of ten randomly chosen lines of D.
melanogaster and one line of D. simulans. Nine of the ten lines are
permissive; D. simulans does not harbor the virus. The melanogaster alleles
contain 4 synonymous changes, 19 noncoding changes, and 13 amino acid
replacement changes, indicating a relatively high level of polymorphism.
Three sequenced restrictive alleles have nearly identical sequences,
indicating that they are relatively young. Compared to the permissive
alleles, they share only a complex deletion at codon 34, CAG-AAT to GGA,
which our analysis indicates to be the site conferring the restrictive
phenotype. Patterns of polymorphism and divergence differ from neutral
predictions by several criteria for the amino terminal region, which
contains the complex deletion (codons 1-91), but not the remainder of the
protein (codons 92-599). We find a higher rate of evolution on the D.
melanogaster lineage than on the D. simulans lineage. The relatively large
amount of both replacement and silent polymorphism in the permissive
alleles and the lack of divergence between permissive and restrictive
alleles suggests that the sigma virus and ref(2)P may be engaged in an
evolutionary race in which new restrictive alleles are continually arising
but are relatively short-lived.
相似文献
27.
Michelle L. Villasmil Christina Gallo-Ebert Hsing-Yin Liu Jamie Francisco 《Cell cycle (Georgetown, Tex.)》2017,16(22):2192-2203
Ceramides and sphingolipid intermediates are well-established regulators of the cell cycle. In the budding yeast Saccharomyces cerevisae, the complex sphingolipid backbone, ceramide, comprises a long chain sphingoid base, a polar head group, and a very long chain fatty acid (VLCFA). While ceramides and long chain bases have been extensively studied as to their roles in regulating cell cycle arrest under multiple conditions, the roles of VLCFAs are not well understood. Here, we used the yeast elo2 and elo3 mutants, which are unable to elongate fatty acids, as tools to explore if maintaining VLCFA elongation is necessary for cell cycle arrest in response to yeast mating. We found that both elo2 and elo3 cells had severely reduced mating efficiencies and were unable to form polarized shmoo projections that are necessary for cell-cell contact during mating. They also lacked functional MAP kinase signaling activity and were defective in initiating a cell cycle arrest in response to pheromone. Additional data suggests that mislocalization of the Ste5 scaffold in elo2 and elo3 mutants upon mating initiation may be responsible for the inability to initiate a cell cycle arrest. Moreover, the lack of proper Ste5 localization may be caused by the inability of mutant cells to mobilize PIP2. We suggest that VLCFAs are required for Ste5 localization, which is a necessary event for initiating MAP kinase signaling and cell cycle arrest during yeast mating initiation. 相似文献
28.
ML Jones 《Biotechnic & histochemistry》2013,88(3):155-159
The discovery of formaldehyde for preserving tissue structures produced a new dimension in microscopy. Preserving structure and morphology became important; therefore, identifying a proper fixing agent for particular structures, chemical entities, and tissues, also became important. The methods for demonstrating tissue structures evolved and were implemented with careful observation and documentation of the results and outcomes. Formalin was incorporated into many techniques, and provided helpful results in many cases and hindrances in others. The effects of formalin on the outcomes of routine and special staining techniques are reported here. 相似文献
29.
The MMS22L–TONSL heterodimer directly promotes RAD51‐dependent recombination upon replication stress 下载免费PDF全文
Wojciech Piwko Karun Mutreja Lepakshi Ranjha Diana Stafa Alexander Smirnov Mia ML Brodersen Ralph Zellweger Andreas Sturzenegger Pavel Janscak Massimo Lopes Matthias Peter Petr Cejka 《The EMBO journal》2016,35(23):2584-2601
Homologous recombination (HR) is a key pathway that repairs DNA double‐strand breaks (DSBs) and helps to restart stalled or collapsed replication forks. How HR supports replication upon genotoxic stress is not understood. Using in vivo and in vitro approaches, we show that the MMS22L–TONSL heterodimer localizes to replication forks under unperturbed conditions and its recruitment is increased during replication stress in human cells. MMS22L–TONSL associates with replication protein A (RPA)‐coated ssDNA, and the MMS22L subunit directly interacts with the strand exchange protein RAD51. MMS22L is required for proper RAD51 assembly at DNA damage sites in vivo, and HR‐mediated repair of stalled forks is abrogated in cells expressing a MMS22L mutant deficient in RAD51 interaction. Similar to the recombination mediator BRCA2, recombinant MMS22L–TONSL limits the assembly of RAD51 on dsDNA, which stimulates RAD51‐ssDNA nucleoprotein filament formation and RAD51‐dependent strand exchange activity in vitro. Thus, by specifically regulating RAD51 activity at uncoupled replication forks, MMS22L–TONSL stabilizes perturbed replication forks by promoting replication fork reversal and stimulating their HR‐mediated restart in vivo. 相似文献
30.
Kroodsma DE Sánchez J Stemple DW Goodwin E Da silva ML Vielliard JM 《Animal behaviour》1999,57(4):855-863
To what extent has the style of song development among songbirds coevolved with other life history strategies? Among Cistothorus wrens in North America, it seems that sedentary or site-faithful habits of marsh wrens, C. palustris, favour song imitation, but seminomadic habits of sedge wrens, C. platensis, favour song improvisation, whereby each male generates a large but unique song repertoire. In this study, we tested whether more sedentary populations of sedge wrens in the Neotropics would imitate songs. At our primary study site near Cartago, Costa Rica, breeding birds were colour-banded during 1995 and 1996, and follow-up surveys revealed that the birds remained at this site the year round. Extensive tape recording and analysis of songs showed that males had large song repertoires (200-300+ songs), and that many songs were shared among neighbouring males. In addition, males only 27 km distant, at La Pastora, used different songs. Furthermore, matched countersinging, in which two males answer each other with identical song types, was recorded near Brasilia, in Brazil. The sharing of songs among permanent neighbours, microgeographical variation in song, and matched countersinging can be achieved only through song imitation, thus revealing a striking difference in the style of song development among different populations of the sedge wren. In the Neotropics, having predictable neighbours throughout life appears to have favoured song imitation, so that individuals can interact using a common, learned code typical of the local population; among more mobile populations in North America, however, individuals improvise large repertoires of species-typical songs, thereby enabling singing males to communicate with any individual, no matter what the population of origin. Strategies of song development must correlate with life history features, and further surveys are needed to make sense of the great diversity of singing behaviours among songbirds. Copyright 1999 The Association for the Study of Animal Behaviour. 相似文献