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PubMed1982

Human monoclonal IgM with autoantibody activity against intermediate filaments.

Monoclonal IgMs from two patients with Waldenström macroglobulinemia were found to react with intermediate filaments. This was shown by (a) immunostaining of various tissues and cultured cells and (b) immunological characterization of the reactive antigen after blotting of polypeptides separated from total cell extracts by gel electrophoresis or purified intermediate filaments on nitrocellulose sheets. One monoclonal IgM had an activity directed only against vimentin, whereas the other reacted with four different classes of intermediate filaments--vimentin, desmin, glial fibrillary protein, and keratins. All of the reactivity of the latter IgM was absorbed by purified vimentin, suggesting that different classes of proteins of intermediate filaments share common antigenic determinant(s). The significance of such autoantibody activity of human monoclonal IgM is discussed in the light of the startling frequency of IgM anti-intermediate filaments antibodies in various diseases.

Antibodies, Monoclonal↗
PubMed1983

Expression of intermediate filaments in ovarian and uterine tumors.

We studied the expression of cytoskeletal intermediate filaments in different types of ovarian and uterine sarcomas and carcinomas. In both uterine and ovarian leiomyosarcomas, in endometrial stromal sarcomas, and also in ovarian sarcomas, most tumor cells appeared to be positive for desmin, the muscle type of intermediate filament protein. In most of the tumors, vimentin was present only in some neoplastic cells and in the vascular endothelia. Interestingly, both uterine and ovarian malignant mixed mesodermal tumors appeared to express several types of intermediate filaments, most of the stromal cells being positive for vimentin or desmin, and the epithelial component expressing keratin. The results show that most of the sarcomatous tumors of the ovary and uterus express mainly muscle type of intermediate filament protein. The results also demonstrate the ability of cells of mesodermal origin to express epithelial cytoskeleton markers--cytokeratins.

Adenocarcinoma↗
PubMedDate not supplied

Cytokeratin intermediate filaments of rat hepatocytes: different cytoskeletal domains and their three-dimensional structure.

A new method of visualizing the three-dimensional architecture of the cytokeratin filaments of the intact rat hepatocyte in situ has been achieved. Frozen sections of liver cut 10 micron thick were serially extracted to remove all elements of the cells except the intermediate filaments. Parallel sections were stained with monoclonal antibodies to the two main cytokeratins found in bile duct and liver cells. Immunofluorescent antibody and immunogold electron microscopy techniques were used to identify the proteins morphologically. Several new observations resulted from these studies. The pericanalicular sheath of intermediate filaments was visualized using steropairs as an uninterrupted branching tubular structure composed of cytokeratins located in the cell cortex of adjacent hepatocytes. Intermediate filaments in the cell cortex formed a distinct sheet of matted filaments which enveloped the entire hepatocyte. The cortical intermediate filaments were in continuity with the pericanalicular sheath and the filaments located within the cytoplasm. The intermediate filaments are attached to the centrioles and appeared to tent the nuclear lamina-pore complex at points of contact. Monoclonal antibodies to rat liver intermediate filament cytokeratins (CK49 and CK55) each stained intermediate filaments located in the cell cortex, within the cytoplasm and at the nucleus. By immunogold staining, some of the intermediate filament filaments were shown to contain both cytokeratins. Filaments which did not stain were thought to be either actin at the cell periphery or nuclear lamins around the nucleus. It is concluded that the cytokeratins form a specialized framework for the cell cortex, canaliculus, centrioles and the nucleus of hepatocytes. The filaments run continuously throughout the cytoplasm without terminating.

Animals↗
PubMed2002

Lens membrane fraction associated intermediate filaments of different aged rats.

PURPOSE: To describe the intermediate filament proteins vimentin, filensin and phakinin associated with different fractions isolated from neonatal, 10 day old and 20 day old rat lenses. METHODS: Fractions were isolated by differential and density gradient centrifugation of lens homogenates from neonatal, 10 day old and 20 day old rats. Aliquots of the 8 M urea soluble proteins of each fraction were separated by SDS PAGE, transferred to PVDF membranes, the membranes were probed with antibodies to vimentin, filensin or phakinin, and analyzed by computer. RESULTS: Over the 20 day growth period, the water soluble fraction increased and the most abundant membrane fraction was characterized by a significant increase in its urea insoluble protein and a significant decrease in its urea soluble protein. There were no significant quantitative changes in any of the other fractions. The concentration of each intermediate filament protein was greatest in the cytoskeletal fraction and over the 20 day period, the amount of vimentin associated with this fraction dramatically decreased, and the amounts of filensin and phakinin dramatically increased. Among the membrane fractions, the greatest concentration of each intermediate filament protein was found in the non sedimenting membrane fraction (NSMF) which was the least abundant fraction recovered. Filensin and phakinin associated with the other three major membrane fractions increased over the 20 day growth period, but the level of vimentin did not significantly change. CONCLUSIONS: The NSMF may represent a domain of the lens plasma membrane particularly important in interaction between plasma membrane and cytoskeleton and as the membrane-cytoskeleton protein architecture of rat lens changes over the first 20 days of life, the changes are readily detected in the different membrane fractions.

Animals↗
PubMed1990

Antibodies to cardiolipin and intermediate filaments: a study of autoimmunity in rheumatoid arthritis.

Autoantibodies to cardiolipin and intermediate filaments have both been reported with increased frequency in rheumatoid arthritis. We evaluated the frequency, pathological significance, and diagnostic relevance of these autoantibodies in a series of 124 patients and controls. We studied 81 patients with rheumatoid arthritis, 23 with osteoarthritis, and 20 normals. Antibodies to cardiolipin were measured by an ELISA method and antibodies to intermediate filaments were measured by indirect immunofluorescence using HEp2 cells. Antibodies to cardiolipin were present in 58% of rheumatoid patients and antibodies to intermediate filaments were present in 55% rheumatoid patients. They were both predominantly of IgM class, and were more frequent than in normal or osteoarthritic controls. Correlating levels of both these autoantibodies to clinical and laboratory measures of disease activity such as Ritchie articular index and C-reactive protein level showed that no consistent relationships existed. They were not related to other auto-antibodies such as rheumatoid factors and anti-nuclear antibodies, nor to each other. These results show that antibodies to cardiolipin and intermediate filaments in rheumatoid arthritis are of no diagnostic value, they are not related to disease activity, and have no relationship to other autoimmune disturbances. We suggest that several pathological mechanisms must be involved in the development of autoantibodies in rheumatoid arthritis.

Adult↗
PubMed1978

Intermediate filaments in nervous tissues.

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.

Animals↗
PubMed1986

Coexistence of cytokeratin, vimentin and neurofilament protein in human choroid plexus. An immunohistochemical study of intermediate filaments in neuroepithelial tissues.

The expression of intermediate filament proteins in human brain ependyma and choroid plexus epithelium has been studied by immunohistochemistry using a panel of monoclonal antibodies directed against all five classes of intermediate filaments. Ependymal cells express GFAP and vimentin filaments, whereas plexus epithelium simultaneously contains neurofilaments, cytokeratins and vimentin, a phenomenon not previously observed in normal cells in vivo. By means of specific antibodies we were able to establish that cytokeratins 8 and 18 but not 19 are present in plexus epithelium.

Aged↗
PubMed2001

[Alterations in neuroepithelial intermediate filaments during neurogenesis in the chick cervical spinal cord].

Intermediate filament proteins including nestin, vimentin and neurofilament were immunohistochemically studied during neurogenesis in the chick cervical spinal cord from stages 8 to 28. At stage 8, neuroepithelial cells of the neural groove contained a large amount of nestin in their cytoplasm and a little vimentin in the basal cytoplasmic areas, and no neurofilaments could be recognized at all. At stage 10, there was a marked decrease in nestin expression in the neural groove, and there was an increase in vimentin in neuroepithelial cells. At stage 15, when the neural tube was formed, small oval neuroblasts appeared in the peripheral area of the neuroepithelium. By employing double-immunostaining, three different neuroblasts could be identified; vimentin-positive and neurofilament-negative cells, neurofilament- and vimentin-double-positive cells, and neurofilament-positive and vimentin-negative cells. During the neuroblast stage, intracellular intermediate filaments were relayed from vimentin to neurofilaments. At stage 20, large polygonal cells containing a large number of neurofilaments could be recognized in the enlarged basal plate of the neural tube. At stage 28, neuronal processes developed in large polygonal cells and, although the staining intensity of the neurofilaments was slightly decreased in the soma, the neuronal processes contained a large number of neurofilaments. During neurogenesis in the chick cervical spinal cord, the intermediate filaments, nestin and vimentin, are present in neuroepithelial cells. During the neuroblast stage, vimentin and neurofilaments are observed together for a short time. Finally, in polygonal neurons, only neurofilaments are observed.

Animals↗
PubMed1981

Isolation of intermediate filaments from rat astrocytes in culture.

Intermediate filaments from rat astrocytes in culture were isolated by subcellular fractionation. The fractionation was monitored by electron microscopy and by quantitative immunoelectrophoresis using rabbit antibody directed against human glial fibrillary acidic protein (GFA). Morphologically intermediate filaments appeared helical with a mean diameter of 10 nm. Isolated filaments were disassembled at highly alkaline pH. After lowering of pH to slightly acidic values reassembled filaments, approximately 17 nm in diameter, were observed. As revealed by sodium dodecyl sulfate polyacrylamide gel electrophoresis the filament preparation was composed predominantly of a 51,000 molecular weight protein, corresponding to GFA. At high loads additional proteins of molecular weights 43,000 and 58,000 were detected. These latter proteins may represent residual actin and vimentin, respectively.

Animals↗
PubMed1983

Differential diagnosis of chordoma, chondroid, and ependymal tumors as aided by anti-intermediate filament antibodies.

Six chordomas, nine chondrosarcomas, and three myxopapillary ependymomas of the filum terminale were evaluated immunohistochemically for the expression of intermediate filament proteins by the use of monospecific antibodies against intermediate filament proteins of keratin, vimentin, and glial fibrillary acidic protein (GFAP) type. All chordomas were positive for keratin but negative for GFAP, whereas chondrosarcomas and ependymomas were negative for keratin. Chondrosarcomas showed strong vimentin positivity, whereas ependymomas were positive for GFAP. Chordomas showed desmosomelike junctions by electron microscopy, whereas chondrosarcomas of different types showed no junctions or only primitive ones. By electron microscopy chordomas often showed prominent intermediate filaments also associated with desmosomes, and poorly differentiated chondrosarcomas also showed prominent intermediate filaments. Keratin positivity of chordomas suggests their epithelial nature, while vimentin positivity of chondrosarcomas is in line with their mesenchymal derivation. The results also show that antibodies against different intermediate filament proteins can be applied as diagnostic aids in making the distinction between chordomas, chondroid tumors, and ependymal tumors.

Adolescent↗
PubMed1984

Electron microscopic study of the in vitro calcium-dependent degradation of Mallory bodies and intermediate filaments in hepatocytes.

Isolated crude fractions of intermediate filaments (IFs) from livers of control and griseofulvin-fed mice were incubated with calcium (Ca2+) or ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid (EGTA). The fractions were semiquantitatively compared using electron microscopy to study the Ca2+-dependent degradation of Mallory bodies and IFs. Numerous intermediate filaments were observed in the cell cortex and cytoplasm of hepatocytes both in control and griseofulvin-fed mice at zero time and after incubation in EGTA. However, only rare IFs near desmosomes were seen after incubation with Ca2+ in the fractions from two control mice. In the remaining controls no IFs survived incubation with Ca2+. Although almost all IFs disappeared after incubation with Ca2+ in griseofulvin-fed mice, some IFs could be detected near desmosomes in all cases. In contrast, Mallory bodies were observed to survive both Ca2+ and EGTA incubations. There was no morphologic difference between the Mallory bodies incubated in Ca2+ or EGTA. The disappearance of IFs after incubation in Ca2+ indicates that the IF's protein of hepatocytes (cytokeratin) can not retain its filamentous structure in the presence of Ca2+. This suggests that Ca2+-dependent factor(s) may regulate IF's degradation. Whether the protein subunits of the IFs were chemically altered was not determined. The resistance of Mallory bodies to Ca2+ dependent degradation suggests that they may form in part as a result of an imbalance in the rate of filament formation and degradation favoring growth of the Mallory body filaments.

Animals↗
PubMed1999

Intermediate filament assembly: temperature sensitivity and polymorphism.

Intermediate filament (IF) proteins are encoded by a large multigene family and form polymers with a uniform diameter of approximately 10 nm. However, although the cytoplasmic representatives all confirm to a unit-type structural principle leading to the formation of extended coiled coils, it is becoming increasingly clear that subunit arrangements and physical properties vary among the different filaments. Thus, the intricate tissue-specific expression pattern of individual IF proteins (especially, their co-expression with other members of the IF protein family or with IF-associated proteins to form obligatory heteropolymers) points to distinct functions acquired during evolution relevant to cellular homeostasis in various tissues.

Amino Acid Sequence↗
PubMed1989

Sea urchin oocytes possess elaborate cortical arrays of microfilaments, microtubules, and intermediate filaments.

Extensive arrays of microfilaments, microtubules and cytokeratin-type intermediate filaments were detected in the cortex of Strongylocentrotus droebachiensis oocytes using fluorescently labeled antibodies on both cortex and whole mount preparations. All three filament systems undergo dramatic structural reorganization during meiotic maturation of the egg. Microfilaments form a dense meshwork within the cortex of the oocyte. After meiosis, the filaments rearrange and shorten, resulting in a more loosely organized network. Both cortical microtubules and microtubules associated with a microtubule-organizing center are observed within the oocyte. After meiosis, the number and length of the cortical microtubules gradually diminish. A microtubule organizing center is found situated between the germinal vesicle and the plasma membrane in many oocytes. A network of filaments extends from the microtubule organizing center and radiates peripherally toward the germinal vesicle, presumably marking the animal pole. Cytokeratin-like intermediate filaments form a reticular network within the oocyte cortex, then solubilize during meiosis. In whole mounts of oocytes there is a single focal center of cytokeratin staining from which filaments radiate. Indirect immunofluorescence experiments, using anti-tubulin and anti-cytokeratin antibodies simultaneously, reveal the intermediate filament focal center to be localized within the microtubule organizing center. These results demonstrate the presence of a complex cortical cytoskeleton in premeiotic eggs of the sea urchin, Strongylocentrotus droebachiensis.

Actin Cytoskeleton↗
PubMed1993

Dynamics of intermediate filaments. Recent progress and unanswered questions.

Intermediate filaments (IFs) have always been considered as the most static and 'skeletal' cellular elements. This view is now changing: new information reveals that IFs exchange subunits at steady-state, that IF networks can be assembled de novo, and that IF proteins are subject to elaborate chemical modification and de-modification during mitosis. I describe below some of the key observations which have made us realize that IFs are dynamic structures. I also discuss some of the remaining questions pertinent to the pathways of IF assembly under in vivo conditions.

Animals↗
PubMed1992

Association of glycosphingolipids with intermediate filaments of mesenchymal, epithelial, glial, and muscle cells.

We reported recently that two glycosphingolipids (GSLs), globoside (Gb4) and ganglioside GM3, colocalized with vimentin intermediate filaments of human umbilical vein endothelial cells. To determine whether this association is unique to endothelial cells or to vimentin, we analyzed a variety of cell types. Double-label immunofluorescent staining of fixed, permeabilized cells, with and without colcemid treatment, was performed with antibodies against glycolipids and intermediate filaments. Globoside colocalized with vimentin in human and mouse fibroblasts, with desmin in smooth muscle cells, with keratin in keratinocytes and hepatoma cells, and with glial fibrillary acidic protein (GFAP) in glial cells. Globoside colocalization was detected only with vimentin in MDCK and HeLa cells, which contain separate vimentin and keratin networks. GM3 ganglioside also colocalized with vimentin in human fibroblasts. Association of other GSLs with intermediate filaments was not detected by immunofluorescence, but all cell GSLs were detected in cytoskeletal fractions of metabolically labelled endothelial cells. These observations indicate that globoside colocalizes with vimentin, desmin, kertain and GFAP, with a preference for vimentin in cells that contain both vimentin and keratin networks. The nature of the association is not yet known. Globoside and GM3 may be present in vesicles associated with intermediate filaments (IF), or bound directly to IF or IF associated proteins. The prevalence of this association suggests that colocalization of globoside with the intermediate filament network has functional significance. We are investigating the possibility that intermediate filaments participate in the intracellular transport and sorting of glycosphingolipids.

Animals↗
PubMed1983

Presence of fibroblast-type intermediate filaments (vimentin) and absence of neurofilaments in pigmented nevi and malignant melanomas.

The cytoskeletal intermediate filaments of pigmented nevi and malignant melanomas (nine cases of each) were evaluated using monospecific antibodies against intermediate filament proteins and immunofluorescence microscopy. Both pigmented nevi and cutaneous malignant melanomas showed only vimentin-type intermediate filaments, but not keratin, neurofilaments, desmin or glial fibrillary acidic protein. Thus, nevi and melanomas do not show neural characteristics in the cytoskeletal intermediate filament pattern although they appear to show other neural markers. Vimentin - content in melanomas versus keratin - content in carcinomas may be used as a differential diagnostic feature.

Desmin↗
PubMed1989

Diagnosis of major tumor categories in fine-needle aspirates is more accurate when light microscopy is combined with intermediate filament typing. A study of 403 cases.

Intermediate filament (IF) typing of tumor cells with monoclonal antibodies was applied to 403 fine-needle aspirates. In 271 cases specific cytologic diagnosis of tumor type was apparent from clinical data and light microscopic study alone. Intermediate filament typing confirmed the tumor type in 262 cases and changed an erroneous cytologic diagnosis of major tumor type in nine cases. In a second group of 132 difficult cases, where the tumor type could not be revealed with certainty, IF typing confirmed the cytologic suggestion of tumor type in 50 cases, changed it in nine cases, and helped resolve ambiguities in cytologic diagnosis in 59 cases. It did not help in 14 cases. Thus IF typing adds independent objective differentiation specific information to descriptive tumor typing currently used in aspiration cytologic study. When combined with the morphologic analysis of tumor cells and clinical information it can refine the cytologic diagnosis of major tumor types and prevent error.

Adolescent↗
PubMedDate not supplied

Immunofluorescence demonstrates the distribution of actin, myosin and intermediate filaments in cultured neuroblastoma cells.

Monolayers of cultured neuroblastoma cells were examined for immunofluorescent reactivity with antibodies directed against actin, myosin or intermediate filaments. In well spread cells, antibody to intermediate filaments stained an intricate cytoplasmic network which extended as filament bundles into cell processes; in poorly spread or rounded cells, the antibody stained thick juxtanuclear filament bundles. By contrast, antibodies to actin or myosin reacted with microspikes and with axonal growth cones. The different topographical distribution of actin, myosin and intermediate filaments suggests that while actin and myosin may have roles in axon elongation, intermediate filaments may function as an internal cytoskeleton as well as in axoplasmic transport. The different distribution of intermediate filaments in well spread compared with rounded cells suggests that the cell makes its filaments prior to axon development and that the filaments subsequently unwind and migrate into the cell processes to form the axon skeleton.

Actins↗