Filament hum extractions

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• The Filament Sensor for Near Real-Time Detection of Cytoskeletal Fiber Structures
• Tau Filament Self-Assembly and Structure: Tau as a Therapeutic Target
• Introducing intermediate filaments: from discovery to disease
• Enilsa brown daryl cyst
• Genetic Origins of Cataract
• Cryo-EM structures of tau filaments from Alzheimer’s disease with PET ligand APN-1607
• Getting rid of heater hum

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The Filament Sensor for Near Real-Time Detection of Cytoskeletal Fiber Structures

Review Series Free access Phone: ; Fax: ; E-mail: john. Find articles by Eriksson, J. Find articles by Dechat, T. Find articles by Grin, B. Find articles by Helfand, B. Find articles by Mendez, M. Find articles by Pallari, H. Find articles by Goldman, R. Published July 1, - More info.

It took more than years before it was established that the proteins that form intermediate filaments IFs comprise a unified protein family, the members of which are ubiquitous in virtually all differentiated cells and present both in the cytoplasm and in the nucleus.

However, during the past 2 decades, knowledge regarding the functions of these structures has been expanding rapidly. Many disease-related roles of IFs have been revealed. In some cases, the molecular mechanisms underlying these diseases reflect disturbances in the functions traditionally assigned to IFs, i. However, many disease conditions seem to link to the nonmechanical functions of IFs, many of which have been defined only in the past few years.

Intermediate filaments IFs represent one of the main cytoskeletal systems found in virtually all vertebrate cells. Depending upon the cell type, IFs are composed of different members of the cytoskeletal IF protein family Figure 1.

IF proteins are also present in the nucleus, where they are the main components of the nucleoskeleton. Overview of the IF protein family. B Based on central rod domain amino acid sequences, net acidic charge, and secondary structure predictions, cytoskeletal IF proteins were grouped into 4 sequence homology classes types I—IV.

Nuclear IF proteins, the lamins, constitute a fifth class. The sixth class of IF proteins also referred to as orphans , beaded filament structural protein 1 Bfsp1; also known as filensin and Bfsp2 also known as phakinin and CP49 , form highly specialized IFs found only in the lens of the eye. Based on their abilities to copolymerize, the IF proteins of the 6 types are further subdivided into assembly groups 1—3.

In this Review we present a historical overview of the discovery and characterization of cytoplasmic and nuclear IFs. Furthermore, we explore many of the features of cytoplasmic IFs that underlie their relevance to disease Table 1 , including their dynamic properties and participation in cytoskeletal crosstalk as well as their roles in signaling, mechanical stabilization, and motility. Although IFs have been studied in various species, such as squid, Xenopus laevis , and Caenorhabditis elegans , we focus here mainly on data obtained from studies in mammalian systems.

Early difficulties in the recognition of IFs as a distinct cytoskeletal system. Retrospectively, the first observations of IFs were made by cytologists and histologists during the period when silver staining was used to generate contrast for observations with bright-field microscopy. For example, the structures called tonofibrils that were described in various silver-stained epithelial tissues 1 were likely the same tonofibrils described much later with antibodies directed against keratin 2 and that we now know are composed of densely packed bundles of IFs see below.

Interest in the composition of natural fibers also stimulated early studies of IFs, which began with X-ray diffraction analyses of human hair, sheep wool, and porcupine quills 3. EM studies provided the first ultrastructural details of bundles of IFs tonofibrils in thin sections of wool, hair, and various epithelial cells, including epidermal keratinocytes 5. Over the next 20 years or so, EM revealed fibers with an average diameter of approximately 10 nm in many cell types — including those comprising skeletal, smooth, and cardiac muscle; those forming epithelial tissues, such as the epidermis; and those found in nerve tissue — as well as in cultured cells such as fibroblasts 6 — In addition to the variety of names, alternate hypotheses regarding the origins of the nm filaments delayed the recognition of IFs as a unique protein family.

For example, it was suggested that IFs were an alternately assembled form of microtubules MTs. This idea arose from EM observations that MT inhibitors, such as colchicine and colcemid, apparently increased the number of nm filaments coincident with MT depolymerization 13 , However, we now know that after MT depolymerization, some types of IFs retract from the cell surface and reorganize into large bundles around the nucleus 8 , 9 , 15 , At the time, it was suggested that the IFs within the bundles were another polymerized form of tubulin 13 , Further confusion regarding the differences between IFs and MTs stemmed from the fact that the major IF protein in fibroblasts, vimentin, has a molecular weight similar to that of tubulin, which made them difficult to separate by gel electrophoresis 17 , In addition, it was even considered for a brief period that IFs contained a microfilament core 19 , However, Ishikawa et al.

This suggestion was supported by other studies in nonmuscle cells 8. By the mid- to late s, several different types of IFs had been isolated, solubilized, and purified by cycles of assembly and disassembly in vitro 21 — These studies took advantage of the unique properties of IFs, namely, that they are insoluble under physiological conditions and are able to repolymerize after disassembly into their subunits under conditions that would irreversibly denature many proteins.

Furthermore, in contrast to actin and tubulin, IFs do not require nucleoside triphosphates such as ATP or GTP for assembly, but rather self assemble under very simple conditions. Classifying IFs. As IF research progressed, it became evident that different cell types possessed different types of cytoskeletal IF proteins For instance, epithelial cells contain mainly keratins; muscle cells, desmin; mesenchymal cells, vimentin; and neurons, neurofilaments Figure 1 B.

It also became apparent that some cell types express more than one IF protein Figure 2 , and that the expression of IF proteins is frequently developmentally regulated e. Because of this, classifying IFs based on cell type—specific expression patterns was difficult. According to this classification, type I cytoskeletal IF proteins are the acidic keratin proteins, and type II cytoskeletal IF proteins are the neutral-basic keratin proteins.

The type IV IF proteins include nestin, synemin, and the neurofilament triplet proteins. Coexistence of distinct keratin and vimentin IFs in an individual cell.

Human alveolar carcinoma cells were processed for immunofluorescence using antibodies against K18 A and vimentin B. C Merged image of A and B. D Phase contrast image. Type V IFs: the nuclear lamins. The nuclear lamins are the major components of a filamentous layer, the nuclear lamina, that is closely associated with the inner nuclear membrane. This layer was originally described in ultrastructural studies of the protozoans Amoeba proteus 28 , 29 and Gregarina melanoplus 30 , as well as in neurons of the leech Hirudo medicinalis 31 , 32 , and often appeared to have a honeycomb structure.

The first descriptions of a fibrous lamina in vertebrate cells came from EM observations of smooth muscle cells obtained from the guinea pig epididymis, intestinal epithelial cells from the Congo eel, and interstitial cells from the cat These studies revealed a to nm fibrous lamina between the inner nuclear membrane and the underlying peripheral heterochromatin. Several other laboratories described a similar structure, which became known as the nuclear lamina, in various cell types and species 34 , These cell-free preparations also revealed that the nuclear lamina is persistent throughout the entire nuclear periphery as a nm layer 37 , 38 , as had been observed in situ 33 , Further biochemical characterization of these proteins, eventually named lamins A, B, and C according to their descending weights 40 , revealed that they were closely related structurally, with lamins A and C sharing extensive sequence homology 41 , This latter finding suggested that lamin C might be a cleavage product of lamin A However, later studies showed that lamins A and C are encoded by different mRNAs, although they are derived from a single gene LMNA by alternative splicing reviewed in ref.

Furthermore, it was discovered that lamin A is first expressed as a precursor protein pre-lamin A , which is posttranslationally processed to become mature lamin A reviewed in ref. With respect to lamin B, it was shown that in vertebrate somatic cells, there are 2 isoforms, lamin B1 and lamin B2, encoded by different genes Similar to lamin A, lamins B1 and B2 are synthesized as precursors and subsequently modified into their mature forms Although at least one lamin isoform appears to be present in all metazoan cells, lamins, at least as we have defined them, seem to be absent from unicellular organisms and from plants reviewed in refs.

It is also of interest to note that comparison of the gene structures of lamin genes and genes encoding cytoplasmic IFs suggests that all IF proteins are derived from a lamin-like progenitor 47 , Early cross-linking experiments showed that the nuclear lamins can form oligomeric structures 42 , Even before the nuclear lamins were recognized as members of the IF protein family, sucrose-gradient density centrifugation and gel-filtration analyses of solubilized fractions of nuclear lamina preparations led to the hypothesis that the basic building blocks of lamin structures were rod-shaped dimers This was supported 3 years later by the finding that lamins belong to the IF protein family, most of which are assembled from rod-shaped, parallel, and in-register dimers 51 — Because of structural differences between the rod domains of lamins and those of cytoplasmic IF, lamins were designated as type V IF proteins 27 , The generation of distinct antibodies specific for each of the lamins led to the observation that lamins A, B, and C localize mainly to the periphery of interphase nuclei Figure 3 and that the nuclear lamina is reversibly disassembled during mitosis 40 , 56 , Further studies revealed that the disassembly of the nuclear lamina during mitosis requires the phosphorylation of lamins at specific sites by several kinases, including p34 cdc2 reviewed in ref.

Lamin localization at the nuclear periphery and within the nucleoplasm. C Differential interference contrast DIC image of the cell, shown to visualize the nucleus. D Merged image. Little is known about the actual structure of the nuclear lamina and of lamins in an intact nucleus. Early EM studies of the nuclear lamina of germinal vesicles from Xenopus oocytes revealed an orthogonal network of regularly spaced to nm fibers 51 , whereas in mammalian cells, only irregular filamentous meshworks have been observed 59 , Besides their presence at the nuclear periphery, lamins have also been described in the nucleoplasm Figure 3 reviewed in ref.

Beginning in , a series of studies demonstrated roles for lamins in DNA replication, DNA transcription, DNA repair, cell signaling, cell proliferation, and cell differentiation as well as in the structural, functional, and epigenetic organization of chromatin Furthermore, it has recently been revealed that mutations in LMNA are associated with many different diseases Table 1 reviewed in ref.

The diversity of lamin-associated processes suggests that the lamins are major components of a nuclear structural framework necessary for the assembly of multiprotein complexes involved in various nuclear functions.

With the generation of specific antibodies and the widespread use of immunofluorescence, it soon became obvious that cytoskeletal IF networks formed extensive, complex arrays that pervaded most of the cytoplasm of cultured cells 17 , These IF networks were presumed by numerous investigators to be static, an assumption based on the finding that after extraction of cells in solutions containing relatively high concentrations of salts and detergents, IFs are retained, while most other cellular proteins including tubulin and actin are extracted In addition, there are relatively small pools of cytosolic soluble IF proteins 63 , which suggested to some that there is very little subunit exchange within IFs.

However, beginning in the late s, studies revealed that ectopically expressed keratin and vimentin readily became incorporated into endogenous IFs through a process termed dynamic subunit exchange 64 , Similar results were obtained when IF proteins were microinjected into cultured cells 66 , Soon after, advances in live cell imaging technology permitted assays of IF subunit exchange in vivo using fluorescence recovery after photobleaching FRAP; refs.

The results of these FRAP studies confirmed that subunit exchange took place all along the length of vimentin and keratin IFs Figure 4 , providing evidence that they are apolar in vivo.

Subsequent studies have demonstrated specific phosphorylation sites that are involved in regulating the dynamic exchange of subunits reviewed in refs. The phosphate turnover maintaining this dynamic exchange is driven by a high protein phosphatase activity on IFs, something that is also necessary for maintaining the structural integrity of IF polymers 73 , Further evidence supporting the dynamic properties of IFs have been derived from observations of mesenchymal cells treated with MT-depolymerizing drugs such as colchicine.

As MTs disappear, IFs move toward the center of the cell, where they form a perinuclear cap 8 , 9 , 15 , There is also evidence showing that this colchicine-induced IF reorganization requires ATP and microfilaments, which suggests that it is driven by molecular motors 75 — The redistribution of IFs from a perinuclear cap into the cytoplasmic extensions that form in spreading fibroblasts also suggested early on that IFs are involved in spreading and shape formation 9.

Vimentin subunit exchange as determined by FRAP.

Tau Filament Self-Assembly and Structure: Tau as a Therapeutic Target

Hymenolepiasis is caused by two cestodes tapeworm species, Hymenolepis nana the dwarf tapeworm, adults measuring 15 to 40 mm in length and Hymenolepis diminuta rat tapeworm, adults measuring 20 to 60 cm in length. Hymenolepis diminuta is a cestode of rodents infrequently seen in humans and frequently found in rodents. Eggs of Hymenolepis nana are immediately infective when passed with the stool and cannot survive more than 10 days in the external environment. When eggs are ingested by an arthropod intermediate host various species of beetles and fleas may serve as intermediate hosts , they develop into cysticercoids, which can infect humans or rodents upon ingestion and develop into adults in the small intestine. A morphologically identical variant, H. When eggs are ingested in contaminated food or water or from hands contaminated with feces , the oncospheres contained in the eggs are released.

Introducing intermediate filaments: from discovery to disease

Cytoskeletal networks control organelle subcellular distribution and function. Herein, we describe a previously unsuspected association between intermediate filament proteins and the adaptor complex AP AP-3 and intermediate filament proteins cosedimented and coimmunoprecipitated as a complex free of microtubule and actin binding proteins. Concomitant with these architectural changes, and similarly to APnull mocha cells, fibroblasts lacking vimentin were compromised in their vesicular zinc uptake, their organellar pH, and their total and surface content of AP-3 cargoes. However, the total content and surface levels, as well as the distribution of the transferrin receptor, a membrane protein whose sorting is AP-3 independent, remained unaltered in both AP and vimentin-null cells. Based on the phenotypic convergence between AP-3 and vimentin deficiencies, we predicted and documented a reduced autophagosome content in mocha cells, a phenotype previously reported in cells with disrupted intermediate filament cytoskeletons. Adaptor complexes play a central role in membrane protein traffic by regulating the packing of membrane proteins into distinct vesicle carriers Bonifacino and Traub, ; Robinson, Four distinct heterotetrameric adaptor complexes AP-1 to AP-4 carry out compartment-selective sorting and vesiculation Bonifacino and Traub, ; Robinson,

Enilsa brown daryl cyst

Review Series Free access Phone: ; Fax: ; E-mail: john. Find articles by Eriksson, J. Find articles by Dechat, T. Find articles by Grin, B.

Genetic Origins of Cataract

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Cryo-EM structures of tau filaments from Alzheimer’s disease with PET ligand APN-1607

McCullagh, Matthew W. Kemp, Catherine Moorwood, Diane L. Sherman, Matthew Burgess, Kay E. Davies; Syncoilin modulates peripherin filament networks and is necessary for large-calibre motor neurons. J Cell Sci 1 August ; 15 : — Syncoilin is an atypical type III intermediate filament IF protein, which is expressed in muscle and is associated with the dystrophin-associated protein complex. Here, we show that syncoilin is expressed in both the central and peripheral nervous systems.

Getting rid of heater hum

By Rob Robinette. Here's my technique for troubleshooting a tube guitar amplifier. Many of these techniques apply to solid state amps too.

This is an open access article distributed under the terms of Creative Commons Attribution License. Epidermolysis bullosa simplex EBS belongs to a group of inherited disorders characterized by the high occurrence of bullous lesions after a certain degree of friction or trauma. The protein products of these genes, keratin 5 and keratin 14, are paired intermediate filaments expressed in basal keratinocytes that contribute to mechanical stability of keratin filament networks 1 , 2. Its cardinal features include large, generalized blisters, mucous membrane involvement, and dystrophic nails.

Acta Neuropathologica Communications volume 7 , Article number: 31 Cite this article. Metrics details. Insights into tau molecular structures have advanced significantly in recent years. Tau structure covers various species as the tau protein itself takes many forms. We will here address a range of studies that help to define the many facets of tau protein structures and how they translate into pathogenic forms. New results shed light on previous data that need now to be revisited in order to up-date our knowledge of tau molecular structure.

Shiels A, Hejtmancik JF. Genetic Origins of Cataract. Arch Ophthalmol. Cataract, which can be defined as any opacity of the crystalline lens,results when the refractive index of the lens varies significantly over distances approximating the wavelength of the transmitted light.