SEARCH · PubMed Health

Results for “fiber development”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,081 records · Page 60Linked to original sources

PubMed2000

Epithelioid leiomyosarcoma in a non-immunocompromised infant: additional differential diagnosis of pediatric "round cell tumors".

We report an 18-month-old Japanese girl with purely epithelioid leiomyosarcoma presenting as a huge intraabdominal mass. The patient had been well from birth and had shown no signs of immunodeficiency. She was negative for human immunodeficiency virus. Blood examination revealed elevated serum neuron specific enolase (NSE). Histologically, the tumor was comprised of solid growths of round or polygonal cells with vesicular nuclei and often vacuolated cytoplasm rich in glycogen. The tumor cells were positive for vimentin, NSE, and MIC2, and were negative for desmin and neurofilament. The age, clinical presentation, and histologic findings mostly favored Ewing's sarcoma/primitive neuroectodermal tumor. Silver stain, however, demonstrated well-developed reticulin fibers often outlining individual tumor cells. An expanded panel of immunostains showed that the tumor cells were intensely positive for smooth muscle actin, and ultrastructural study revealed abundant fine cytoplasmic filaments with focal subsarcolemmal densities, various amounts of glycogen, and irregularly arranged, thick basal lamina. The diagnosis of epithelioid leiomyosarcoma was made. Following reduction in tumor size by chemotherapy, the serum NSE level was normalized. From the surgical finding, the primary site was presumed to be the urachus or the urinary bladder dome. Although extremely rare, epithelioid leiomyosarcoma should be added in the list of differential diagnoses of pediatric "round cell tumors."

Abdominal Neoplasms↗

PubMedDate not supplied

Topical vanadate optimizes collagen organization within granulation tissue.

Systemic ingestion of vanadate, a nonspecific inhibitor of tyrosine phosphatases, doubles wound breaking strength, enhances the packing of collagen fibers, and prevents the appearance of myofibroblasts in granulation tissue. Will the local application of vanadate mimic the systemic effects? Pairs of polyvinyl alcohol sponges, each with a central reservoir and attached injection port, were subcutaneously implanted in rats. Daily, one implant received 0.2 ml of saline and the other received 0.2 ml of 0.03 mM vanadate in saline. On day 7, harvested sponges had equivalent wet weights. The vanadate-treated sponges had fibroblasts separated by connective tissue, with a more intense birefringence of the collagen fibers. Transmission electron microscopy showed collagen more uniformly packed in the vanadate treated sponges where collagen fibers were equally spaced and had equal diameters. By immunohistology, myofibroblasts, defined by the expression of alpha-smooth muscle actin within stress fibers, were absent in vanadate-treated granulation tissue. The expression of alpha-smooth muscle actin was restricted to smooth muscle cells of blood vessels. Controls had densely packed alpha-smooth muscle actin staining myofibroblasts, weak birefringence, and randomly spaced collagen fibers with irregular diameters. We conclude that the local application of vanadate prevents the appearance of myofibroblasts and optimizes the organization of collagen fibers in developing granulation tissue.

Administration, Topical↗

PubMed2001

Use of conditionally immortalized mouse cardiac fibroblasts to examine the effect of mechanical stretch on alpha-smooth muscle actin.

Mechanical stretch regulates alpha-smooth muscle actin (SMA) expression in myofibroblasts but limited replication and cellular heterogeneity have hampered definitive studies in vitro. We examined the role of applied force in regulating SMA expression in conditionally immortalized cardiac fibroblast lines derived from H-2Kb-tsA58 transgenic mice. When plated in differentiating conditions (37 degrees C without interferon-gamma), transgenic myofibroblasts exhibited vimentin staining, no desmin staining and abundant SMA in well-developed stress fibers that were indistinguishable from controls. Magnetically-generated tensile forces (approximately 500 pN/cell) applied through collagen-coated magnetite beads selectively reduced SMA but not beta-actin mRNA and protein content in both cell types. The early loss of SMA was due in part to selective leakage into the cell culture medium. Depolymerization of actin filaments with cytochalasin D blocked the force-induced reduction of SMA. Cardiac fibroblast lines established from H-2Kb-tsA58 transgenic mice provide a phenotypically stable source of cells for studying the role of physical forces in regulating SMA.

Actins↗

PubMed1992

Congenital polyneuropathy in Walker-Warburg syndrome.

Polyneuropathy was found in a patient with the Walker-Warburg syndrome. The most dominant features were the presence of extremely and tortuously proliferated myelin sheaths, the most of which having no neurofilaments and neurotubules. The other peculiar findings were the presence of microfilaments in Schwann cell cytoplasms, which were very similar to neurofilaments, and the presence of partial and abrupt disappearance of myelin sheaths. The severity of neuropathy was variable among nerve bundles, and a few nerve bundles looked normal on light microscopy. The above-mentioned lesions did not suggest the degeneration and/or regeneration of normally developed nerve fibers. We could not conclude the pathogenesis of this neuropathy, however, it was logical to consider that they reflected dysplastic myelination due to Schwann cell dysmaturity as well as the cerebral dysplasia.

Axons↗

PubMed2004

GABA-mediated giant depolarizing potentials as coincidence detectors for enhancing synaptic efficacy in the developing hippocampus.

Spontaneously occurring neuronal oscillations constitute a hallmark of developmental networks. They have been observed in the retina, neocortex, hippocampus, thalamus, and spinal cord. In the immature hippocampus, the so-called "giant depolarizing potentials" (GDPs) are network-driven synaptic events generated by gamma-aminobutyric acid (GABA), which at this stage is depolarizing and excitatory. We have tested the hypothesis that during the first postnatal week, GDP-associated calcium signals may alter the properties of synaptic transmission at poorly developed mossy fiber (MF)-CA3 connections. We found that "pairing" GDPs with MF stimulation induced a persistent increase in synaptic efficacy at MF-CA3 synapses. When the interval between GDPs and MF stimulation was increased, the potentiating effect progressively declined and disappeared. The potentiation depended on activation of voltage-dependent calcium channels and calcium flux. This activity may contribute to the refinement of neuronal connectivity before the establishment of the adult neuronal circuit.

Animals↗

PubMed1977

Solid-like character of virus solutions.

The solid-like behavior of turnip yellow mosaic virus solutions following the extrusion of viral RNA in alkali was observed with a torsion-fiber balance developed for the purpose. This method provided a direct measurement of the yield stresses required to break or liquefy these solutions. The yield stresses were found to increase and to be less time dependent with increasing concentrations of the virus and they were maximal at room temperatures. If the virus had been damaged, as by freeze-thaw, little or no solid-like behavior could be demonstrated. Purified viral capsids, with or without added RNA, were also inactive. The values for the yield stresses were of the same order as the value reported previously with the use of a magnetic suspension viscometer; hence, the apparent coherency appears unrelated to the magnetic fields generated by the latter instrument. These solutions behaved as typical liquids after the required stress was applied [about 0.005 to 0.17 dyne cm-2 (0.05 to 1.7 micronN cm-2)], these forces being smaller than those usually conferred by ordinary handling.

Freezing↗

PubMed1979

Fibronectin and the multiple interaction model for platelet-collagen adhesion.

A rapid, sensitive, and reproducible assay to determine the adhesion of platelets to collagen has been developed. Collagen fibers and adherent platelets are retained on polycarbonate membrane filters. Chemical modification of collagen by acetylation and of platelets by treatment with chymotrypsin markedly reduces adhesion. The role of fibronectin in the collagen-platelet interaction has been examined. Treatment of platelets with purified antibody or Fab' fragments to fibronectin only slightly reduces adhesion. Preincubation of platelets with high concentrations of gelatin reduces adhesion by only 22% but fails to inhibit aggregation. Thus, fibronectin has only a limited role in the adhesion of platelets to collagen and is either not involved in the adhesion that leads to aggregation or is only one of several adhesion mechanisms, any of which alone can initiate aggregation.

Animals↗

PubMed1993

Caldesmon and a 20-kDa actin-binding fragment of caldesmon inhibit tension development in skinned gizzard muscle fiber bundles.

Caldesmon is known to inhibit actin-activated myosin ATPase activity in solution, to inhibit force production when added to skeletal muscle fibers, and to alter actin movement in the in vitro cell motility assay. It is less clear that caldesmon can inhibit contraction in smooth muscle cells in which caldesmon is abundant. We now show that caldesmon and its 20-kDa actin-binding fragment are able to inhibit force in chemically skinned gizzard fiber bundles, which are activated by a constitutively active myosin light-chain kinase in the presence and absence of okadaic acid. This inhibitory effect is reversed by high concentrations of Ca2+ and calmodulin. Therefore, caldesmon may act by increasing the level of myosin phosphorylation required to obtain full activation. Our results also suggest that caldesmon does not act to maintain force in smooth muscle by cross-linking myosin with actin since competition of binding of caldesmon with myosin does not cause a reduction in tension.

Actins↗

PubMed1995

A membrane-associated form of sucrose synthase and its potential role in synthesis of cellulose and callose in plants.

Sucrose synthase (SuSy; EC 2.4.1.13; sucrose + UDP reversible UDPglucose + fructose) has always been studied as a cytoplasmic enzyme in plant cells where it serves to degrade sucrose and provide carbon for respiration and synthesis of cell wall polysaccharides and starch. We report here that at least half of the total SuSy of developing cotton fibers (Gossypium hirsutum) is tightly associated with the plasma membrane. Therefore, this form of SuSy might serve to channel carbon directly from sucrose to cellulose and/or callose synthases in the plasma membrane. By using detached and permeabilized cotton fibers, we show that carbon from sucrose can be converted at high rates to both cellulose and callose. Synthesis of cellulose or callose is favored by addition of EGTA or calcium and cellobiose, respectively. These findings contrast with the traditional observation that when UDPglucose is used as substrate in vitro, callose is the major product synthesized. Immunolocalization studies show that SuSy can be localized at the fiber surface in patterns consistent with the deposition of cellulose or callose. Thus, these results support a model in which SuSy exists in a complex with the beta-glucan synthases and serves to channel carbon from sucrose to glucan.

Amino Acid Sequence↗

PubMed1996

Higher plants contain homologs of the bacterial celA genes encoding the catalytic subunit of cellulose synthase.

In spite of much effort, no one has succeeded in isolating and characterizing the enzyme(s) responsible for synthesis of cellulose, the major cell wall polymer of plants. We have characterized two cotton (Gossypium hirsutum) cDNA clones and identified one rice (Oryza sativa) cDNA that are homologs of the bacterial celA genes that encode the catalytic subunit of cellulose synthase. Three regions in the deduced amino acid sequences of the plant celA gene products are conserved with respect to the proteins encoded by bacterial celA genes. Within these conserved regions, there are four highly conserved subdomains previously suggested to be critical for catalysis and/or binding of the substrate UDP-glucose (UDP-Glc). An overexpressed DNA segment of the cotton celA1 gene encodes a polypeptide fragment that spans these domains and binds UDP-Glc, while a similar fragment having one of these domains deleted does not. The plant celA genes show little homology at the N- and C-terminal regions and also contain two internal insertions of sequence, one conserved and one hypervariable, that are not found in the bacterial gene sequences. Cotton celA1 and celA2 genes are expressed at high levels during active secondary wall cellulose synthesis in developing cotton fibers. Genomic Southern blot analyses in cotton demonstrate that celA forms a small gene family.

Acetobacter↗

PubMed2001

Laminin-10/11 and fibronectin differentially regulate integrin-dependent Rho and Rac activation via p130(Cas)-CrkII-DOCK180 pathway.

The alpha(5) chain-containing laminin isoforms, laminins-10 and -11 (laminin-10/11), are the major components of the basement membrane, having potent cell-adhesive activity. We examined the cell-adhesive and integrin-mediated signaling activities of laminin-10/11 in comparison to fibronectin, the best characterized extracellular adhesive ligand. We found that laminin-10/11 are more active than fibronectin in promoting cell migration and preferentially activate Rac, not Rho, via the p130(Cas)-CrkII-DOCK180 pathway. Cells adhering to fibronectin develop stress fibers and focal contacts, whereas cells adhering to laminin-10/11 do not, consistent with the high cell migration-promoting activity of laminin-10/11. Pull-down assays of GTP-loaded Rac and Rho demonstrated the preferential activation of Rac on laminin-10/11, in contrast to the activation of Rho on fibronectin. Activation of Rac by laminin-10/11 was associated with the phosphorylation of p130(Cas) and an increased formation of a p130(Cas)-CrkII-DOCK180 complex. Cell migration on laminin-10/11 was suppressed by the expression of either a dominant-negative Rac or CrkII mutants defective in p130(Cas) or DOCK180 binding. This is the first report demonstrating a distinct activation of Rho family GTPases resulting from adhesion to different extracellular ligands.

Cell Movement↗

PubMed2002

Protein kinase C and calcium/calmodulin-activated protein kinase II (CaMK II) suppress nicotinic acetylcholine receptor gene expression in mammalian muscle. A specific role for CaMK II in activity-dependent gene expression.

Nicotinic acetylcholine receptor (nAChR) gene expression is regulated by both muscle activity and increased intracellular calcium. This regulation is an important developmental event that rids receptors from the extrajunctional region of the developing muscle fiber. In avian muscle, it has been proposed that muscle activity suppresses nAChR gene expression via calcium-activated protein kinase C (PKC)-dependent phosphorylation of the myogenic transcription factor, myogenin. Here, we examined the role that PKC and other kinases play in mediating calcium- and activity-dependent suppression of nAChR genes in rat primary myotubes. We found that although activated PKC could regulate nAChR promoter activity and transiently suppressed both nAChR and myogenin gene expression, it did not appear to be required for calcium- or activity-dependent control of nAChR gene expression in mammalian muscle. Neither depletion of PKC from myotubes nor specific pharmacological inhibition of PKC blocked the suppression of nAChR gene expression produced by calcium or muscle depolarization. In contrast, we provide evidence that calcium/calmodulin-activated protein kinase II participates in mediating the effects of muscle depolarization on nAChR and myogenin gene expression.

Animals↗

PubMed1997

Quantification and regulation of mRNAs encoding beaded filament proteins in the chick lens.

PURPOSE: To quantify the expression of beaded filament protein mRNA levels in regions of the chick lens and to examine the in vitro regulation of message and protein levels using cell culture techniques. METHODS: RNase protection assays and Northern blotting were used to quantify beaded filament protein mRNA levels in dissected lenses. Cultured cells were assayed for mRNA with RNase protection and for protein with Western blotting and ELISA techniques after treatment with cAMP analogs. RESULTS: Beaded filament protein message levels were greatly up-regulated in cortical fiber cells compared to annular pad cells. Full length messages were also detected in nuclear fiber cells. The presence of an unusual form of the CP49 message with a lamin-like insert, CP49INS, was also established. Both message and protein levels were subject to regulation in response to elevated intracellular cAMP levels. CONCLUSIONS: The accumulation of beaded filament protein levels during fiber cell development may be due to the increased cAMP-mediated transcription of message. The presence of CP49INS may lend new insight into mechanisms of intermediate filament assembly.

Animals↗

PubMed1978

The inertial behavior of fibers.

The inertial deposition is given considerable credit in the deposition of inhaled particulate matter in the upper respiratory tract. A determination of the parameters governing the impaction of fibers must be the basis of evaluating the role of impaction in the respirability of fibrous dusts. The study reported here describes an experimental method of defining the inertial behavior of fibers. The results of the experiments show that the aspect ratio of the fibers plays a much more important role than hitherto considered. The results of the experimental work gave an empirical mathematical model for the prediction of the impaction of fibers from the physical properties of fibers such as density, fiber diameters and aspect ratio. In addition an equivalent diameter based on inertial properties of the fiber is developed.

Aerosols↗

PubMed2005

The neuromuscular junction: anatomical features and adaptations to various forms of increased, or decreased neuromuscular activity.

The neuromuscular junction (NMJ) allows communication between motor neurons and muscle fibers. During development, marked morphological changes occur as the functional NMJ is formed. During the postnatal period of rapid growth and muscle enlargement, endplate size concurrently increases. Even beyond this period of pronounced plasticity, the NMJ undergoes subtle morphological remodeling--expansion and retraction--although its overall dimensions remain stable. This natural, continual NMJ remodeling is amplified with alterations in neuromuscular activity. Increased activity, presented by exercise training, typically results in expansion of NMJ size. Disuse, brought about by neurotoxins, denervation, or spaceflight, also elicits substantial reconfiguring of the endplate.

Acetylcholine↗

PubMed1979

Low calorie bulking agents.

Obesity, a common disorder causing excess mortality due to the development of cardiovascular disease, hypertension, respiratory illness, and diabetes, is difficult to control by simple dieting techniques. Low calorie foods, which can facilitate newer weight reduction approaches such as behavior modification, often lack adequate palatability due to the absence of carbohydrate or fat. Various low calorie bulking agents that can replace the traditionally used carbohydrates and fats are discussed in terms of caloric value, utility, and regulatory status. Methods of measuring caloric utilization of bulking agents in test animals and humans are evaluated. For fat, no really satisfactory replacement is currently available, although several promising are under development. Dietary fiber sources such as microcrystalline cellulose are receiving considerable attention as flour replacements. While the polyols have many desirable attributes, as sucrose replacements, their caloric utilization values generally prevent a significant caloric reduction when they are used in foods. Several experimental sucrose replacements are described.

Adult↗

PubMed1986

Localization of low-sulfur keratin proteins in the wool follicle using monoclonal antibodies.

Monoclonal antibodies that recognize components of the low-sulfur keratin proteins extracted from Merino wool have been used to locate these components within the wool follicle. Immunoblotting procedures showed that all of the monoclonal antibodies bound more than one of the eight low-sulfur protein components, indicating that these proteins have antigenic determinants in common. Immunofluorescence studies showed that those antibodies specific for the component 7 family of the low-sulfur proteins bound to the developing wool fiber, whereas those antibodies recognizing the component 8 family bound to areas throughout the wool follicle, particularly the inner and outer root sheaths, but also to the fiber, the cuticle, and the epidermis. One of the monoclonal antibodies also bound to intermediate filament networks of cultured human epithelial cells.

Animals↗

PubMed1988

Motor neurons contain agrin-like molecules.

Molecules antigenically similar to agrin, a protein extracted from the electric organ of Torpedo californica, are highly concentrated in the synaptic basal lamina of neuromuscular junctions in vertebrate skeletal muscle. On the basis of several lines of evidence it has been proposed that agrin-like molecules mediate the nerve-induced formation of acetylcholine receptor (AChR) and acetylcholinesterase (AChE) aggregates on the surface of muscle fibers at developing and regenerating neuromuscular junctions and that they help maintain these postsynaptic specializations in the adult. Here we show that anti-agrin monoclonal antibodies selectively stain the cell bodies of motor neurons in embryos and adults, and that the stain is concentrated in the Golgi apparatus. We also present evidence that motor neurons in both embryos and adults contain molecules that cause the formation of AChR and AChE aggregates on cultured myotubes and that these AChR/AChE-aggregating molecules are antigenically similar to agrin. These findings are consistent with the hypothesis that agrin-like molecules are synthesized by motor neurons, and are released from their axon terminals to become incorporated into the synaptic basal lamina where they direct the formation of synapses during development and regeneration.

Acetylcholinesterase↗