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At least 469 records · Page 26Linked to original sources
PubMed1995

Biosynthesis of type VI collagen by glioblastoma cells and possible function in cell invasion of three-dimensional matrices.

The biosynthesis of type VI collagen was studied in human glioblastoma cell line, U-87 MG. The effects of ascorbic acid on type VI collagen synthesis and secretion were investigated. After ascorbic acid treatment, type VI collagen in cell layers increased from 4.48% in control to 6.63% in the ascorbic acid treated cultures, an increase of 48%. The effect of ascorbic acid on type VI collagen synthesized by glioblastoma cells was lower than that reported for osteosarcoma cells (Engvall et al., 1986). The reason for these differences is still under investigation. The function of type VI collagen in glioblastoma cells is still unknown. We utilized the collagen gel system to elucidate the possible roles of type VI collagen in glioblastoma cells in vitro. Glioblastoma cells in collagen gels showed a stellate shape with long, branched processes in all directions. The strong positive reactivity of type VI collagen detected on cell bodies and cell processes by anti-type VI collagen antibody indicated that this specific collagen was associated with cell surfaces and processes, without releasing or diffusing into the gels. Type VI collagen was directly involved in the cell process extension. When living cells were treated with anti-type VI collagen antibody, a variation of cell morphology was observed. Instead of a stellate shape with processes, cells formed clusters without or with very short processes. These data suggest that type VI collagen, synthesized and secreted by glioblastoma cells, may play a role in tumor cell adhesion and spreading, and enhance cell process extension, penetration, and invasion into collagen gels.

Antibodies↗
PubMed1993

Effect of recombinant tumor necrosis factor-alpha on three-dimensional growth, morphology, and invasiveness of human glioblastoma cells in vitro.

In order to investigate the antiproliferative and anti-invasive effects of tumor necrosis factor (TNF)-alpha on human glioblastoma cells, an in vitro three-dimensional (anchorage-independent) assay was performed using Matrigel, a mixture of extracellular matrix proteins. Four glioblastoma-derived cell lines, including one cloned line, were cultured in Matrigel with or without TNF-alpha. In the Matrigel containing TNF-alpha, three of the four cell lines, including the cloned line, showed significant growth inhibition in a dose-dependent manner. Dramatic three-dimensional morphological differences were observed between TNF-treated and untreated glioblastoma cells cultured in Matrigel. Untreated cells formed large and highly branched colonies throughout the gel. In contrast, the majority of TNF-treated cells demonstrated truncated branching processes and, at a high TNF-alpha dose, an increasing number of cells remained in relatively small spherical aggregates, their cell processes being significantly reduced. Quantitative invasion assay using a micro-Boyden chamber system confirmed that TNF-treated cells lost invasiveness in a dose-dependent manner. These results suggest that TNF-alpha exerts not only antiproliferative but also anti-invasive effects on human glioblastoma cells in vitro. It is believed that this is the first report showing the anti-invasive effect of TNF-alpha on tumor cells.

Brain Neoplasms↗
PubMed2004

Ring vaccination and smallpox control.

We present a stochastic model for the spread of smallpox after a small number of index cases are introduced into a susceptible population. The model describes a branching process for the spread of the infection and the effects of intervention measures. We discuss scenarios in which ring vaccination of direct contacts of infected persons is sufficient to contain an epidemic. Ring vaccination can be successful if infectious cases are rapidly diagnosed. However, because of the inherent stochastic nature of epidemic outbreaks, both the size and duration of contained outbreaks are highly variable. Intervention requirements depend on the basic reproduction number (R0), for which different estimates exist. When faced with the decision of whether to rely on ring vaccination, the public health community should be aware that an epidemic might take time to subside even for an eventually successful intervention strategy.

Contact Tracing↗
PubMed1999

Cells expressing the NG2 antigen contact nodes of Ranvier in adult CNS white matter.

The NG2 antibody, which recognises an integral membrane chondroitin sulphate, labels a significant population of cells in adult CNS white matter tracts of the rat optic nerve and anterior medullary velum (AMV). Adult NG2+ cells are highly complex with multiple branching processes and we show by EM immunocytochemistry that they extend perinodal processes, which contact nodes of Ranvier. NG2+ cells do not react to conventional immunohistochemical markers for adult glia and so we reservedly term them NG2P cells. In vitro, NG2 labels oligodendrocyte-type-2 astrocyte (O-2A) progenitors that can give rise to oligodendrocytes or type-2 astrocytes, depending on the culture medium. Thus, it is possible that NG2P cells may be derived from the same stem cells as oligodendrocytes. Interestingly, NG2+ cells identified previously in adult CNS displayed phenotypic characteristics of O-2Aadult progenitors and it is possible that, like them, NG2P cells might retain the capacity of generating oligodendrocytes in the adult CNS. This may be an important role of NG2P cells in demyelinating diseases such as multiple sclerosis. It is significant therefore that the perinodal processes of NG2P cells contact the only sites of exposed axolemma in myelinated axons, so that NG2P cells are ideally situated to detect and respond to changes in axonal function during demyelination. A further implication of our finding is that NG2P cells may perform functions at nodes of Ranvier previously attributed to perinodal astrocytes, including the clustering and maintenance of sodium channels in the axon membrane at nodes, during development and following demyelination.

Animals↗
PubMed2001

[Roles of the HNK-1 carbohydrate epitope in the nervous system].

The HNK-epitope, 3-sulfo-glucuronyl residue is expressed specifically on a series of cell adhesion molecules and on some glycolipids in the nervous system over a wide range of species, and its expression is spatially and temporally regulated during the development of the nervous system. To study the biological functions of the epitope, we have cloned the enzymes that are involved in the biosynthesis of the epitope, glucuronyltransferase (GlcAT-P and GlcAT-S) and sulfotransferase (Sulf-T), A Northern blot analysis of GlcAT mRNAs in various rat tissues indicated that GlcAT-P and -S are the brain-specific or neural-specific enzymes. Upon transfection of the full length GlcAT-P cDNA into COS-1 cells, which do not express the HNK-lepitope, cells were transformed into HNK-1 positive cells. These cells showed dramatic changes of the cell architecture. They had long and branched processes with irregular shapes and several micro spikes on the soma and processes. Another function of the HNK-1 epitope is the inhibition of cell-cell aggregation. Thus control COS-1 cells formed huge aggregates after incubation at room temperature for 90 min, and most of the HNK-1 positive cells remained as free single cells.

Animals↗
PubMed2003

Structural elements of dynamic RNA strings.

Short transient secondary structures form while RNA is being transcribed, and these become the initial sites for protein anchoring. The insulin gene transcript (IGT) of chain length 1,430 nucleotides can be folded into 92 stem-loops, at an average of one stem-loop per 15.5 nucleotides (range: 9-35). The 25-hydroxyvitamin D3 1-alpha-hydroxylase gene transcript (HDHGT) of 4,825 nucleotides can fold into 274 stem-loops, at one stem-loop per 17.6 nucleotides (range: 9-45). We found no differences in transient secondary structures between the exons of IGT and HDHGT but there were significant differences between the introns. RNA chain shortening by folding ranged from 2.57 to 9.6 fold. Contraction ratios for IGT were 2.79 for minimal contraction and 7.77 for maximal contraction, and for HDHGT 2.57 and 8.80 respectively. The maximal contraction ratios but not the minimal contraction ratios differed significantly between IGT and HDHGT. This implies that initial RNP fibril formation may proceed by shared mechanisms whereas the final degree of compaction can differ in different hnRNPs. Metastable co-transcriptional folding may be necessary for "chaperones"/"match makers" to refold the RNA correctly for splicing and other maturation process. Branch point sequences are not consistent and are not included in the analysis. However, 5' and 3' splice regions have more disordered secondary structures, and 3' and 5' exon regions contain intrinsic snap-back complementarity that can bring 3' and 5' nucleotides together for joining. Upon splicing, the remaining exons undergo no change except for a few stem-loops flanking the splice sites.

25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗
PubMed1992

Rates of decay for the survival probability of a mutant gene.

If qk is the extinction probability of a slightly supercritical branching process with offspring distribution [pkr:r = 0, 1, 2, ...], then it is shown that if supk sigma r r3pkr less than infinity, inf sigma 2k greater than 0, and mk----1, then 1-qk approximately 2(mk - 1)sigma -2k, where mk = sigma r rpkr, sigma 2k = k sigma r r2pkr - m2k. This provides a simple set of sufficient conditions for the validity of a conjecture of Ewens (1969) for the survival probability of a slightly advantageous mutant gene.

Gene Frequency↗
PubMed1990

Ultrastructure of the monkey vas deferens.

The testicular and prostatic ends of the vasa deferentia of two male monkeys weighing 3-4 kg were examined ultrastructurally, using the method described by Richards & Tranzer (1975). The general ultrastructure of the vas deferens resembles that described previously. In addition, new features were observed. These include (i) shedding of parts of the apical portions of the epithelial cells; (ii) darkening of mitochondria-rich cells in the epithelium; (iii) presence of secretory granule-like structures in the principal cells of the epithelium; (iv) mast cells which may be associated with blood vessels or smooth muscle cells, and (v) presence of dense osmiophilic cells in the lamina propria and muscle coat, but predominantly in the former. The last-mentioned cells are stellate, having many branching processes, and are characterised by the appearance of many caveolae on their surface membranes. Basal lamina may or may not be seen to surround the cell membranes. The cells are contacted by nerve varicosities which resemble those of cholinergic and purinergic fibres.

Animals↗
PubMed1990

Responses of astrocytes in culture after low dose laser irradiation.

The effect of Helium-Neon low dose laser on astrocytes was investigated in cultures of isolated astrocytes from albino neonatal rats. The laser appeared to inhibit the growth of astrocytes as exemplified by the smaller sizes of the cells and the decreased leucine uptake in each cell after treatment. Temporary decrease in the number of mitoses was also observed, but this trend was reversed soon after. Electron microscopic studies revealed an increase in buddings from cell bodies and processes (branches) after irradiation.

Animals↗
PubMedDate not supplied

Chemical control of growth and morphological characteristics of anaplastic glioma cells.

Nerve growth factor (NGF) and glia maturation factor (GMF) reverse some of the transformed characteristics of T9 glioma cells (Marushige et al., Cancer Res 47: 4109-4115, 1987). As an attempt to define the mechanisms of such actions, various chemical agents which modulate second messenger systems were examined for their effects on growth and morphological characteristics of these cells. Administration of bromo-cAMP, forskolin and methylisobutylxanthine retarded cell growth and induced formation of long, branching processes which were similar to those induced by GMF. Perturbation of Ca2(+)-mediated processes by a Ca2+ ionophore, ionomycin, and by calmodulin antagonists, chlorpromazine and W-7, on the other hand, arrested cell growth, and caused clustering of cells, spreading of the cytoplasm and development of lamellipodium-like protrusions which were reminiscent of the effects of NGF. Administration of bromo-cAMP in combination with chlorpromazine, W-7 or ionomycin prevented spreading of the cytoplasm and produced compact cell bodies with well-developed processes. The results of this study demonstrate that modulation of specific second messenger systems by chemical agents are capable of simulating selective morphological changes inducible by NGF and GMF.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1989

A cell line derived from non-neoplastic human neuroretinal cells.

We have derived a cell line from an epiretinal membrane excised surgically from a premature female infant born at a gestational age of 25 weeks, and who developed stage 5 retinopathy of prematurity. The cell line, which in early passages appeared immunocytochemically to contain cells with both neuronal and glial characteristics, has been maintained in culture for 14 months at the time this manuscript was submitted, and has survived 20 passages. The cells have a diploid, human karyotype, with most cells possessing 46 normal appearing chromosomes, including 44 autosomes and two X-chromosomes. Morphologically, the cell line at early passages consisted of polygonal cells and also of cells possessing long, spindly branching processes. These two cell types were cloned. Nearly 100% of the cells of both morphologic types in mixed cultures stained immunocytochemically for neuron-specific enolase (NSE), a neuronal marker, and approximately 5-10% of the cells in mixed cultures (including about 50% of the cells with the spindly morphology, that were less prevalent in mixed cultures) stained for glial fibrillary acid protein (GFAP), a glial marker. We have not performed "double-label" immunocytochemistry, but it was evident from the proportion of cells that stained with each marker that many cells must contain both GFAP and NSE. At least 50% of the cells in most of the early cultures were positive for keratin, while all were (and remain) negative for muscle actin. No cells are found that are immunocytochemically positive for factor VIII, a vascular endothelial cell marker. These cultured cells have also been studied immunocytochemically for their production of extracellular matrix substances. The cultures are immunocytochemically positive for type IV (but not type I) collagen, laminin and fibronectin. In later passages, cells of both clones lost their immunocytochemical positivity for GFAP and NSE, and all became positive for keratin. Cells of both clones also developed a similar, polygonal morphology, lacking long processes. By electron microscopy, many of the cells were seen to possess nonmotile cilia, with a 9 + 0 pattern of microtubule doublets. This cell line may be useful for studies of human retinal cell development and metabolism, and responses to pathological processes.

Cell Division↗
PubMed1988

Oligodendrocytes and CNS myelin are nonpermissive substrates for neurite growth and fibroblast spreading in vitro.

To study the interaction of neurons with CNS glial cells, dissociated sympathetic or sensory ganglion cells or fetal retinal cells were plated onto cultures of dissociated optic nerve glial cells of young rats. Whereas astrocytes favored neuron adhesion and neurite outgrowth, oligodendrocytes differed markedly in their properties as neuronal substrates. Immature (O4+, A2B5+, GalC-) oligodendrocytes were frequently contacted by neurons and neurites. In contrast, differentiated oligodendrocytes (O4+, A2B5-, GalC+) represented a nonpermissive substrate for neuronal adhesion and neurite growth. When neuroblastoma cells or 3T3 fibroblasts were plated into optic nerve glial cultures, the same differences were observed; differentiated oligodendrocytes were nonpermissive for cell adhesion, neurite growth, or fibroblast spreading. These nonpermissive oligodendrocytes were characterized by a radial, highly branched process network, often contained myelin basic protein, and may, therefore, correspond to cells actively involved in the production of myelin-like membranes. Isolated myelin from adult rat spinal cord was adsorbed to polylysine-coated culture dishes and tested as a substrate for peripheral neurons, neuroblastoma cells, or 3T3 cells. Again, cell attachment, neurite outgrowth, and fibroblast spreading was strongly impaired. General physicochemical properties of myelin were not responsible for this effect, since myelin from rat sciatic nerves favored neuron adhesion and neurite growth as well as spreading of 3T3 cells. These results show that differentiated oligodendrocytes express nonpermissive substrate properties, which may be of importance in CNS development or regeneration.

Animals↗
PubMedDate not supplied

[Structural organization of an identified giant neuron of Helix lucorum].

Method of intracellular staining with cobalt was used for detailed study of processes branching of the giant cell in the left parietal ganglion of the snail Helix lucorum L. Dendritic and axonal branches are described and quantitatively characterized. Terminals of axonal collaterals of this neurone innervating presumed neurosecretory bodies are described in the tissue surrounding the ganglion.

Animals↗
PubMedDate not supplied

[Ultrastructural characteristics of the salivary glands of of the tick Ixodes persulcatus. II. Type III alveoli of the sucking female].

Electron microscope observations were conducted to study changes in the cellular structure of IIId type alveoli of feeding females of I. persulcatus. Within the first 1-2 days of feeding granulosecreting glandular cells "d" and "e" get free of secretory inclusions. After that cells "d" degenerate completely and cells "e" undergo morphological transformations and start to fulfil osmoregulatory functions. From the third day of feeding cytoplasm of cells "e" and basal intersticial cells form a complex labyrinth from a system of branching processes limiting intercellular space from the basal to apical surfaces of alveolar wall. Cells "e" of I. persulcatus in their structure and functional activity closely resemble the earlier described cells "f" in alveoli III of the tick Rhipicephalus appendiculatus.

Animals↗
PubMed1982

Calculation of the equilibrium distribution for a deleterious gene by the finite Fourier transform.

In a population of constant size every deleterious gene eventually attains a stochastic equilibrium between mutation and selection. The individual probabilities of this equilibrium distribution can be computed by an application of the finite Fourier transform to an appropriate branching process formula. Specific numerical examples are discussed for the autosomal dominants, Huntington's chorea and chondrodystrophy, and for the X-linked recessive, Becker's muscular dystrophy.

Female↗
PubMed1984

Glial fibrillary acidic protein-like immunoreactivity in the iris: development, distribution, and reactive changes following transplantation.

Using immunohistochemistry with antisera raised against the glial fibrillary acidic protein (GFA), we have studied the appearance and distribution of GFA-like immunoreactivity in whole mounts of rodent iris and in sectioned cat and cow iris. In the adult rat iris, a dense plexus of GFA-positive fibers was seen in both the dilator plate and the sphincter. The fluorescent fibers formed large meandering bundles and a dense irregular network of thinner fibers. In the sphincter, mainly thinner fibers were seen. Thin fibers were also seen winding around blood vessels in the dilator plate. In adult mouse iris, the GFA-positive fibers had a quite different distribution with a few radially oriented fiber bundles superimposed on a more regular network of thinner fibers. Adult guinea pig irides showed still another pattern of GFA-positive fibers with a low number of bundles and thinner fibers forming a sparse irregular network. In thicker fiber bundles of all three rodent species, as well as at branching sites of the thinner fibers, negative or weakly fluorescent swellings surrounded by GFA-like immunoreactivity were present. These structures probably represent the cellular origin of the GFA-positive fibers. Thick, strongly fluorescent fiber bundles, as well as numerous thinner fibers, were seen in sections of cat and cow iris. Prenatally, fibers were visualized at embryonic day 18 in the rat. In these irides as well as in irides from 21-day-old embryos and 1-day-old pups, most fibers were organized in a gradually increasing system of thin meandering fiber bundles that showed limited branching. At postnatal day 6, a more mature network of thinner fibers had developed between the now more numerous fiber bundles. No obvious increase or decrease in the amount of GFA-positive fibers was seen in irides grafted to the anterior eye chamber of adult rat recipients examined 1 and 6 days after grafting. However, in these irides, as well as in the host irides, strongly fluorescent spider-like cells with short branching processes and a negative nucleus were seen. These cells were more numerous and more strongly fluorescent in grafted irides as compared to recipient irides and in the 6-day iris grafts as compared to the 2-day grafts. In all probability, the GFA-positive fibers and cells forming a network in adult irides from different species and in embryonic and grafted rat irides represent Schwann cells and their processes. The cellular origin of the spider-like cells in the iris grafts is less clear.

Animals↗
PubMed1977

Fitting a model to the growth of yeast colonies.

When yeast cells reproduce, scars are left on the parent cell where the offspring has budded. Using a branching process model, it is possible to obtain the expectations of numbers of cells with 0, 1, 2, ... offspring. In this paper, theoretical results are tested against empirical data for three types of yeast cells. We examine the hypothesis that birth and death rates of cells with no previus offspring may differ from those of cells with one or more offspring. It is suggested that the oscillatory empricial results for the proportions of cells with 0, 1, 2, 3 and 4 offspring may be due to different mean budding times for these cells.

Models, Biological↗