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L T Furcht

Publications and source records attributed to L T Furcht.

At least 145 records · Page 8Linked to original sources
PubMed1980

An axial periodic fibrillar arrangement of antigenic determinants for fibronectin and procollagen on ascorbate treated human fibroblasts.

Fibronectin and collagens are major constituents of the cell matrix of fibroblasts. Fibronectin is a 220,000 dalton glycoprotein that mediates a variety of adhesive functions of cells examined in vitro. Fibronectin is secreted in a soluble form and interacts with collagen to form extracellular filaments. Fibronectin and procollagen type I were localized using the peroxidase anti-peroxidase method. Under standard culture conditions, fibronectin and procollagen were localized to non-periodic 10 nm extracellular fibrils, the cell membrane and plasma membrane vesicles. Ascorbate treatment of cells leads to a new larger fibril with a diameter of approximately 40 nm. Antibodies to fibronectin and procollagen I react to these native collagen fibrils with an axial periodicity of approximately 70 nm. Fibronectin is clearly associated with native collagen fibrils produced by ascorbate treated cells and there is an asymetric distribution or segregation of fibronectin on these collagen fibrils with a 70 nm axial repeat.

Ascorbic Acid↗
PubMed1980

Fibronectin presence in native collagen fibrils of human fibroblasts: immunoperoxidase and immunoferritin localization.

Fibronectin is a major constituent of the fibroblast extracellular matrix. Fibronectin binds to collagen, mediates fibroblast adhesion to collagen, and is synthesized and secreted into the medium of cultured fibroblasts. Affinity-purified antibodies to fibronectin and collagen were localized using the peroxidase-antiperoxidase method or with ferritin-coupled secondary antibodies. Using human fibroblasts cultured under routine conditions, fibronectin and procollagen I react in a nonperiodic manner with: 1) approximately 10 nm extracellular fibrils, 2) cell membrane, and 3) membrane-associated vesicles. All fibrils react with both antibodies, suggesting some form of codistribution of fibronectin and collagen in these fibrils. Treatment with ascorbate leads to the development of a larger diameter extracellular fibril, approximately 40 nm in diameter. These large diameter fibrils are clearly collagen fibrils as documented by the procollagen antibody reaction. Importantly, fibronectin is bound to or a constituent of these "native" or cellular made collagen fibrils. Fibronectin and procollagen antibodies localized with the peroxidase-antiperoxidase method have a 70 nm axial repeat of reaction product on ascorbate-treated fibroblasts. Localization of antibodies with ferritin-labeled secondary antibodies is less satisfactory, but supports the basic observations made with the unlabeled antibody enzyme method. This observation rules out any potential criticisms. Although it is more difficult to observe with immunoferritin, there is an indication that antibodies to fibronectin react with an axial periodicity on cellular produced collagen fibrils.

Collagen↗
PubMed1980

Ascorbate-induced fibroblast cell matrix: reaction of antibodies to procollagen I and III and fibronectin in an axial periodic fashion.

Fibronectin and procollagen types I and III are constituents of the extracellular matrix of human fibroblasts. Ultrastructural immunocytochemistry using the peroxidase anti-peroxidase method showed fibronectin and procollagen antibodies reacting in continuous fashion on 10 nm diameter extracellular fibrils on human fibroblasts. Intracellular localization showed an intense accumulation of procollagen within cells cultured under routine conditions. This accumulation appeared almost as if there were a blockade in secretion of procollagen under routine culture conditions. Cells treated with ascorbic acid do not have the dense intracellular accumulation of procollagens seen with the apparent blockade of secretion in cells cultured under routine conditions. Ascorbate treated cells also have a more pronounced extracellular accumulation of matrix fibronectin and procollagen constituents. At the electromicroscopic level a new 40 nm diameter fibril is formed after ascorbic acid treatment of human fibroblasts. Antibody to fibronectin and procollagen I and III are seen binding to the 40 nm diameter fibrils in a periodic or stuttered appearance. The fibronectin and procollagen antibodies react with a 70 nm axial repeat along these 40 nm fibrils formed after ascorbate treatment. These studies suggest that under routine culture conditions "precursor" fibrils of fibronectin and procollagen are formed. Ascorbic acid treatment leads to enhanced matrix formation. Ultrastructural studies clearly show antibodies to fibronectin bind to fibronectin on native collagen fibrils formed by human fibroblasts cultured with ascrobic acid. Lastly there is an asymmetric or 70 nm axial periodic distribution of fibronectin along these definitive or mature collagen fibrils formed after ascorbic acid treatment.

Antibodies↗
PubMed1979

Reversal by glucocorticoid hormones of the loss of a fibronectin and probollagen matrix around transformed human cells.

Confluent cultured human skin fibroblasts had an extracellular fibrillar matrix of fibronectin and procollagen. Human skin fibroblasts transformed by SV40 did not have such a matrix. Treatment of transformed fibroblasts with 10(-5) to 10(-8) M dexamethasone and 10(-5) to 10(-7) M cortisol, but not testosterone or progesterone, caused partial restoration of the matrix. Glucocorticoid-treated transformed human fibroblasts can serve as a model for partial reversion toward normal or differentiation of transformed human fibroblasts.

Cell Membrane↗
PubMed1978

Changes in intramembranous particle topography and concanavalin A receptor mobility associated with myoblast differentiation.

These studies have examined the distribution of plasma membrane intramembranous particles (PMP) visualized by freeze fracture and concanavalin A receptors seen by ultrastructural cytochemistry of differentiated and undifferentiated L6 myoblasts. Undifferentiated mononucleated cells have a clustered distribution of PMP on the majority of the fracture faces. Associated with cell differentiation and cell fusion a more uniform distribution of PMP is observed. Changes also occur with myoblast differentiation in the topography and dynamics of receptors bound to concanavalin A. If undifferentiated or differentiated cells are fixed with glutaraldehyde and then reacted with con-A a uniform distribution of con-A is seen on the cell surfaces. In contrast to this if unfixed live cells are reacted at 37 degrees C with con-A a profound redistribution occurs on differentiated cells (greater than 99% showing redistribution) while receptors remain in a uniform array on undifferentiated cells (approximately 95% uniform distribution). In addition to the membrane binding, con-A is observed to bind to an extracellular filamentous matrix seen in high density undifferentiated cultures which then appears to be degraded with differentiation and myoblast fusion. These studies show that a number of membrane changes, both structural and dynamic occur with myoblast differentiation.

Cell Differentiation↗
PubMed1978

Effects of cell density and transformation on the formation of a fibronectin extracellular filamentous matrix on human fibroblasts.

We have studied normal and transformed cultured human fibroblasts by ultrastructural immunocytochemistry with antibodies to fibronectin (the large external transformation-sensitive glycoprotein). Human fibroblasts at low density have very little extracellular material organized into a filamentous form. A diffuse membrane component of low-density fibroblasts reacts with fibronectin antibodies. As normal fibroblasts grow to confluence, an extensive extracellular filamentous matrix forms. The filaments are 15 to 20 nm in diameter, lack periodicity, and frequently occur in a meshwork. Antibody to fibronectin reacts with these filaments as well as with a diffusely distributed membrane component. Cultures of SV40-transformed human fibroblasts lack the extracellular filamentous matrix reacting with fibronectin antibodies; however, fibronectin is detected on plasma membranes. These studies indicate that a major difference between normal and transformed human fibroblasts is the failure of transformed fibroblasts to form a fibronectin-containing extracellular filamentous matrix.

Cell Adhesion↗
PubMed1977

Cell surface changes accompanying myoblast differentiation.

Myoblasts are mononucleated cells and associated with differentiation undergo cell fusion and become multinucleated. The current studies have examined cell surface dynamic changes of Concanavalin A lectin receptor mobility and the role of hormones in modulating myoblast differentiation. A uniform distribution of Con-A receptors is observed in undifferentiated cells when reacted with Con-A at 37 degrees C. Cells from differentiating cultures or fully differentiated myotubes reacted similarly at 37 degrees C show a significant redistribution of Con-A into patches, "caps," and endocytic vesicles containing Con-A. If undifferentiated and differentiated cells are first prefixed with glutaraldehyde then reacted with Con-A continuous distribution of Con-A is seen across the cell surface. This suggests redistribution of Con-A and its receptors occurs in differentiated cells reacted with lectin at 37 degrees C. It is further shown that insulin (10 microgram/ml) significantly enhances myoblast differentiation but that this occurs after an apparent stimulation of proliferation. In contrast to insulin, dexamethasone (10 micron and 100 micron) profoundly inhibits myoblast differentiation while having different effects on proliferation; 10 micron dex stimulates cell growth while 100 micron dex suppresses cell proliferation. Lastly, an extracellular filamentous matrix which binds Con-A is observed at the ultrastructural level in high density cultures. No significant redistribution of Con-A is observed on this matrix in distinction to the redistribution observed on the cell membrane in differentiated cells.

Cell Differentiation↗
PubMed1977

Plasma membrane intramembranous particle topography in 3T3 and SV3T3 cells: the effect of cytochalasin B.

The topography of plasma membrane intramembranous particles in contact-inhibited and transformed cells is a topic of current controversy. We have reported that particles are aggregated in 3T3 cells and that they are randomly distributed in SV3T3 cells. Other investigators have, however, proposed that these differences result from the effect of cryoprotectants and are blocked by aldehyde fixation. The experiments described in this paper re-examine PMP topography in large samples of 3T3 and SV3T3 cells prepared by a variety of preparative methods. The results confirm that 3T3 cells contain aggregated intramembranous particles and that native SV3T3 cells do not, regardless of whether cells are prepared in glycerol, sucrose, tissue culture medium or following prefixation in paraformaldehyde. Data presented in this paper also show that cytochalasin B induces dose- and time-dependent disaggregations of particles in contact-inhibited 3T3 cells. Particle disaggregation results from exposure of cells in situ for 1-3 h to 1-500 ng/ml cytochalasin B. Removal of the drug by washing with reincubation of cells in medium containing serum results in particle reaggregation within 1 to 3 h. These observations suggest that intramembranous particles in 3T3 cells are aggregated in the native state and that membrane-active drugs modulate their distribution by a mechanism possibly involving disruption of linkages between membrane components and the cytoskeleton.

Animals↗
PubMed1976

Membrane pathology of normal and malignant cells--a review.

The plasma membrane has been shown to play a critical role in the regulation of cell growth and proliferation, and pathologic change in the plasma membrane has been detected in neoplastic cells. This article reviews the structure and functions of biological membranes and discusses the differences that have been reported in the plasma membranes of normal and malignant cells that may be associated with neoplastic transformation.

Animals↗
PubMed1976

Independent alterations in cell shape and intramembranous particle topography induced by cytochalasin B and colchicine in normal and transformed cells.

Native differences in cell shape and plasma membrane organization in contact-inhibited and transformed cells and the effects of cytochalasin B and colchicine on these cells have been examined by scanning electron microscopy and freeze fracture-electron microscopy. Confluent BALB/c 3T3 cells show a flat, polygonal shape with limited cell overlapping, some microvilli, and plasma membranes with an aggregated distribution of intramembranous particles. Simian virus 40-transformed BALB/c 3T3 cells, by contrast, have a pleomorphic, bipolar spindle shape, extensive cell overlapping, more numerous surface projections, and a random distribution of intramembranous particles. Treatment of 3T3 and SV3T3 cells with 10(-6) M colchicine produced changes in cell shape and induced intramembranous particle aggregation in SV3T3 cells but did not significantly affect the freeze fracture morphology of 3T3 plasma membranes. Treatment of 3T3 and SV3T3 cells with cytochalasin B (1 mug/ml) also produced marked changes in cell shape and induced intramembranous particle disaggregation in 3T3 cells, but it did not affect intramembranous particle distribution in SV3T3 cells. Lower doses of colchicine (10(-9) M) or cytochalasin B (1 to 50 ng) modulated intramembranous particle distribution in transformed and normal 3T3 cells, respectively, without seriously affecting cell shape. These results are interpreted to suggest that modulation of cell shape or cell surface topography and intramembranous particle distribution are separable phenomena.

Animals↗