Duration of anticoagulation for deep-vein thrombosis and pulmonary embolism.
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Anticoagulants↗
Biomedical subjects
D Muir
Publications and source records attributed to D Muir.
Arctic contaminants: sources, occurrence and pathways.
Potentially toxic organic compounds, acids, metals and radionuclides in the northern polar region are a matter of concern as it becomes evident that long-range transport of pollution on hemispheric to global scales is damaging this part of the world. In this review and assessment of sources, occurrence, history and pathways of these substances in the north, the state of knowledge of the transport media--the ocean and atmospheric circulation--is also examined. A five-compartment model of the northern region is developed with the intent of assessing the pathways of northern contaminants. It shows that we know most about pathways of acids, metals and radionuclides and least about those of complex synthetic organic compounds. Of the total annual inputs of anthropogenic acidic sulphur and the metals lead and cadmium to the Arctic via the atmosphere, an estimated 10-14% are deposited. A water mass budget for the surface layer of the Arctic Ocean, the most biologically active part of that sea, is constructed to examine the mass budget for one of the major persistent organochlorine compound groups found in remote regions, hexachlorocyclohexanes (HCH), one isomer of which is lindane. It is concluded that both the atmosphere and the ocean are important transport media. Even for the HCH substances which are relatively easily measured and simple in composition compared to other synthetic organics, we know little about the occurrence and environmental physical/chemical characteristics that determine pathways into the food chain. More environmental measurements, chemical characterization studies and environmental chemical transport modelling are needed, as is better knowledge of the circulation of the Arctic Ocean and the marine food web.
Acids↗
The localization of nerve growth factor-like immunoreactivity in the adult rat basal forebrain and hippocampal formation.
The role of nerve growth factor (NGF) as a target derived neurotrophic agent for specific cell populations in the peripheral nervous system has been well documented and much evidence suggests that NGF may serve a similar neurotrophic role in the CNS supporting the cholinergic neurons of the basal forebrain. Previous attempts to localize NGF by immunocytochemical methods, however, have not yielded evidence confirming the regional distribution expected based upon reported levels of extractable NGF. In the present study, affinity purified polyclonal antibodies to beta-NGF and a modified immunohistochemical protocol were used to demonstrate specific NGF-like immunoreactivity in the adult rat hippocampal formation and basal forebrain. In the hippocampal formation, NGF-like immunoreactivity was localized primarily within the hilus of the dentate gyrus and within stratum lucidum of the CA3 and CA2 hippocampal subfields. Staining appeared to be associated with cell processes and was similar to the reported distribution of mossy fibers suggesting that granule cells may either serve as a primary source of hippocampal NGF or that mossy fibers selectively accumulate NGF produced by other cell populations. In the basal forebrain, NGF-like immunoreactivity was localized within neuronal cell bodies of the medial septum, diagonal band, and nucleus basalis of Meynert and was further demonstrated to colocalize exclusively with LNGF-R positive neurons. These findings demonstrate the presence of an NGF-like antigen in association with cholinergic neurons of the basal forebrain and strongly support the hypothesis that NGF may serve as an endogenous trophic factor for this adult neuronal population.
Animals↗
Reduced ciliary neuronotrophic factor-like activity in nerves from diabetic or galactose-fed rats.
This study examined the levels of ciliary neuronotrophic factor (CNTF)-like activity in the sciatic nerve of rats with short-term streptozotocin-induced diabetes or dietary supplementation with 40% galactose. CNTF-like activity, found in nerve extracts by in vitro bioassay, was reduced to 20% of control values after 1 or 2 months of galactose feeding (both P less than 0.01) and to 70% of control values after two months of streptozotocin diabetes (P less than 0.01). These data demonstrate that short-term hyperglycemia or its consequences can reduce extractable levels of Schwann cell-derived neuronotrophic factor and raise the possibility that impaired Schwann cell production of CNTF may contribute to the development of experimental diabetic neuropathy.
Animals↗
Immunolocalization of ciliary neuronotrophic factor in adult rat sciatic nerve.
Two rabbit polyclonal antibodies were raised against synthetic peptides corresponding to residue numbers 45-59 and 181-200 of rat ciliary neuronotrophic factor (CNTF). The resulting antibodies were purified by affinity chromatography and both purified antibodies reacted by enzyme-linked immunoassay (ELISA) and immunoblotting with rat sciatic nerve CNTF. The anti-CNTF peptide antibodies were used to immunostain sections of adult rat sciatic nerve, previously known as the richest tissue source of CNTF. By light microscopy both antibodies appeared to stain exclusively Schwann cells and axons and both did so with the same pattern of specific staining. Immunostaining was eliminated by absorption of the anti-peptide antibodies with either their corresponding peptide or with purified rat nerve CNTF or by using purified nonspecific IgG. Schwann cells were stained and in semi-thin sections this staining appeared to be in the Schwann cell cytoplasm. Axons could be stained in addition to Schwann cells providing higher concentrations of antibodies were used. Epineurial, endoneurial and endothelial cells appeared unstained. Since all Schwann cells and axons appear to contain CNTF and since CNTF is known to act in vitro to support sensory and sympathetic ganglionic and motor neurons, we suggest that Schwann cells may normally provide CNTF to those neurons contributing axons to the peripheral nerve.
Amino Acid Sequence↗
Autocrine inhibition of mitotic activity in cultured oligodendrocyte-type-2 astrocyte (O-2A) precursor cells.
During development, oligodendrocytes are generated from a bipotential glial stem cell, the oligodendrocyte-type-2 astrocyte precursor (O-2A). O-2A cells are under the mitogenic influence of the platelet-derived growth factor (PDGF) released from type-1 astrocytes. In vitro experiments have shown that O-2A cells stimulated by PDGF are limited to a set number of divisions and then differentiate to oligodendrocytes by becoming unresponsive to the growth factor. In the healthy adult central nervous system, oligodendrocyte proliferation remains generally quiescent and is possibly under negative growth control. The view that O-2A lineage cells are capable of negatively regulating their own proliferation is supported by the demonstration that conditioned medium obtained from O-2A cultures inhibits their DNA synthesis. In addition to O-2A cells, the newly established CG4 cell line, a derivative of O-2A cells, was found to inhibit O-2A lineage cell proliferation. The antiproliferative activity was present in the media conditioned by CG4 cells that were expanded as undifferentiated O-2A precursors, as well as by CG4 cells induced to differentiate to nonproliferating oligodendrocytes. Moreover, the inhibitory activity was produced by CG4 cells (source cells) propagated by various mitogens. The inhibition of mitotic activity was nearly complete, dose-dependent, fully reversible, and exhibited when CG4 cells (test cells) were stimulated to divide by various mitogens, such as PDGF, basic fibroblast growth factor, or medium conditioned by the neuronal B104 cell line. The inhibition of proliferation was accompanied by the conversion of the phenotype of CG4 cells, from A2B5+/O4- precursors to A2B5-/O4+ pro-oligodendrocytes.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
CG-4, a new bipotential glial cell line from rat brain, is capable of differentiating in vitro into either mature oligodendrocytes or type-2 astrocytes.
We have established a permanent cell line (CG-4) of rat central nervous system glial precursors from primary cultures of bipotential oligodendrocyte-type 2-astrocyte (O-2A) progenitor cells, which were kept proliferating with the mitogen(s) secreted by the neuronal B104 cell line. The CG-4 cells have a normal karyotype and display the properties of normal O-2A cells. CG-4 cells can be propagated in serum-free culture medium supplemented with medium conditioned by B104 cells for unrestricted periods of time as O-2A cells, characterized by the presence of the A2B5 surface marker and the absence of markers specific for oligodendrocytes (galactocerebroside, myelin basic protein) or type 2-astrocytes (glial acidic fibrillary protein). bFGF and PDGF are potent mitogens for CG-4 cells and their combination can substitute for the B104-derived mitogen(s). CG-4 cells are capable of differentiating into either oligodendrocytes or type 2-astrocytes. Differentiation into oligodendrocytes occurs after withdrawal of the mitogen. Replacement of the mitogen with fetal calf serum (20%), in contrast, induces 50% of the CG-4 cells to differentiate into type 2-astrocytes. Pure cultures of oligodendrocytes or type 2-astrocytes can be generated in substantial amounts from CG-4 cells and maintained for several weeks in medium containing 5% fetal calf serum.
Animals↗
Merosin promotes cell attachment and neurite outgrowth and is a component of the neurite-promoting factor of RN22 schwannoma cells.
The laminin-like protein merosin was purified from human placenta in intact form and as pepsin fragments and compared to laminin in heparin affinity chromatography and cell binding assays. Intact merosin and a small fragment of merosin comprising the last two repeats of the heavy chain g domain bind to heparin. Intact merosin and large pepsin fragments of merosin, but not the small C-terminal fragment, mediate the attachment and spreading of several types of cells and promote neurite outgrowth from neuronal cells similar to laminin and its corresponding fragments. Cells with various integrin-type receptors for laminin attached equally well to merosin and laminin, suggesting that several of the known laminin binding receptors also bind to merosin. Antibodies to the beta 1 subunit of integrins inhibited neurite outgrowth on merosin as well as on laminin, confirming the involvement of integrin-mediated interaction of cells with both merosin and laminin. Schwannoma cells, which have previously been shown to produce a laminin-like, neurite-promoting factor, synthesize merosin in vivo and in vitro as shown by protein and mRNA analysis. The results suggest that merosin, which is the more abundant basement membrane protein in the laminin family, has properties very similar to laminin despite differences in the structure of the heavy chain. Furthermore, merosin may be identical to or a component of the neurite-promoting factors previously reported from heart, muscle, and Schwann cells.
Base Sequence↗
Stromelysin generates a fibronectin fragment that inhibits Schwann cell proliferation.
Our previous report (Muir, D., S. Varon, and M. Manthorpe. 1990. J. Cell Biol. 109:2663-2672) described the isolation and partial characterization of a 55-kD antiproliferative protein found in Schwann cell (SC) and schwannoma cell line-conditioned media and we concluded that SC proliferation is under negative autocrine control. In the present study the 55-kD protein was found to possess metalloprotease activity and stromelysin immunoreactivity. The SC-derived metalloprotease shares many properties with stromelysin isolated from other sources including the ability to cleave fibronectin (FN). Furthermore, limited proteolysis of FN by the SC-derived protease generated a FN fragment which itself expresses a potent antiproliferative activity for SCs. The active FN fragment corresponds to the 29-kD amino-terminal region of the FN molecule which was also identified as an active component in SC CM. Additional evidence that a proteolytic fragment of FN can possess antiproliferative activity for SCs was provided by the finding that plasmin can generate an amino-terminal FN fragment which mimicked the activity of the SC metalloprotease-generated antiproliferative FN fragment. Both the 55-kD SC metalloprotease and the 29-kD FN fragment could completely and reversibly inhibit proliferation of SCs treated with various mitogens and both were largely ineffective at inhibiting proliferation by immortalized or transformed SC lines. Normal and transformed SC types do secrete the proform of stromelysin, however, transformed cultures do not produce activated stromelysin and thus cannot generate the antiproliferative fragment of FN. These results suggest that, once activated, a SC-derived protease similar to stromelysin cleaves FN and generates an antiproliferative activity which can maintain normal SC quiescence in vitro.
Animals↗
Bovine cranial zygomycosis caused by Saksenaea vasiformis.
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Animals↗
An enzyme-linked immunosorbent assay for bromodeoxyuridine incorporation using fixed microcultures.
We report a quantitative method by which a single microculture can be examined for (i) cell morphology; (ii) cell number; (iii) DNA synthesis; and (iv) expression of cell antigens. This method first involves measuring by enzyme-linked immunosorbent assay (ELISA) the total bromodeoxyuridine (BrdU) incorporation into DNA by monolayer microcultures. The BrdU-ELISA measurement was followed by simultaneous immunostaining for BrdU-positive nuclei and for a cytoplasmic antigen. The method was applied to the measurement of mitogen-induced proliferation of rat sciatic nerve Schwann cell and cerebral astroglia microcultures. The ELISA measurement of BrdU incorporation compares favorably with measurements of tritiated thymidine incorporation and offers the additional advantages that the same microculture can subsequently be examined for cell number, for cell morphology, and for the percentage of cells having BrdU-labeled nuclei and other antigens.
Animals↗
Schwann cell proliferation in vitro is under negative autocrine control.
In healthy adult peripheral nerve, Schwann cells are believed to be generally quiescent. Similarly, cultures of isolated rat sciatic nerve Schwann cells hardly proliferate in serum-supplemented medium. The possibility that Schwann cells negatively regulate their own proliferation was supported by the demonstration that conditioned media from Schwann cell cultures inhibited the proliferation of mitogen-stimulated test cultures. The inhibition could be complete, was dose dependent, and was exhibited when the test Schwann cells were under the influence of different types of mitogens such as cholera toxin, laminin, and living neurons. The inhibition of proliferation was completely reversible and a rapid doubling of cell number resulted when treatment with conditioned medium was withdrawn from mitogen-stimulated Schwann cells. Conditioned medium from cholera toxin-stimulated and immortalized Schwann cell cultures contained less antiproliferative activity than that found in medium from quiescent Schwann cell cultures. However, media conditioned by two actively proliferating rat Schwannoma cell lines were rich sources of antiproliferative activity for Schwann cells. Unlike the mitogen-stimulated Schwann cells, whose proliferation could be inhibited completely, the immortalized and transformed Schwann cell types were nearly unresponsive to the antiproliferative activity. The antiproliferative activity in Schwann and Schwannoma cell conditioned media was submitted to gel filtration and SDS-PAGE. The activity exists in at least two distinct forms: (a) a high molecular weight complex with an apparent molecular mass greater than 1,000 kD, and (b) a lower molecular weight form having a molecular mass of 55 kD. The active 55-kD form could be derived from the high molecular weight form by gel filtration performed under dissociating conditions. The 55-kD form was further purified to electrophoretic homogeneity. These results suggest that Schwann cells produce an autocrine factor, which we designate as a "neural antiproliferative protein," which completely inhibits the in vitro proliferation of Schwann cells but not that of immortalized Schwann cells or Schwannoma lines.
Animals↗
Rat sciatic nerve Schwann cell microcultures: responses to mitogens and production of trophic and neurite-promoting factors.
During embryonic development and in response to injury, the growing axons of peripheral neurons may influence the migration and proliferation of Schwann cells which, in return, may present neurons with a critical supply of factors required for neuronal survival, growth and differentiation. The identification and characterization of agents influencing the proliferation of Schwann cells as well as Schwann cell production of factors affecting neurons is greatly facilitated by the use of in vitro techniques. We describe here a simplified method of obtaining large numbers of purified neonatal rat sciatic nerve Schwann cells for use in generating large numbers of replicate microcultures. We then illustrate the use of these microcultures to examine Schwann cell: i) morphology and survival; ii) proliferation; and iii) production of neuronotrophic and neurite-promoting activities. We report that rat Schwann cells in microculture proliferate in response to serum, laminin and fibronectin, cholera toxin, and chick embryo parasympathetic ciliary neurons. Also, extracts of Schwann cell microcultures contain independently regulated activities which support the survival and neurite outgrowth of peripheral ganglionic neurons.
Animals↗
Growth cone advance mediated by fibronectin-associated filopodia is inhibited by a phorbol ester tumor promoter.
In serum-supplemented medium, exposure to the tumor promoter 4 beta-phorbol 12 beta-myristate 13 alpha-acetate (PMA) increases the proportion of SH-SY5Y neuroblastoma cells with neurites and increases the average neurite length. In the present study, under serum-free conditions, PMA treatment had the opposite effects, i.e., retarded neurite sprouting and partially inhibited neurite elongation. This inhibition in neurite outgrowth was partially antagonized by the addition of serum fibronectin (FN) to the medium or substratum. In the absence of PMA, SH-SY5Y cells grown under serum-free conditions showed extensive neurite outgrowth as well as the capacity to secrete FN into their microenvironment and form FN-containing substratum-attachment sites. Immunogold labeling and whole mount transmission electron microscopy (WMTEM) demonstrated FN-containing contact pads at sites where filopodia attached to the substratum and focal plaques on the underside of growth cone margins. The appearance and abundance of FN-containing contact pads and focal plaques were increased by the addition of exogenous FN to defined medium. Focal plaques appeared in close association with microfilament bundles, and nearly always with bundles that projected into filopodia attached to the substratum by contact pads. A method for immunolabeling FN in the filopodial contact pads of living cultures provided more direct evidence that filopodia and contact pads have a major role in FN-mediated attachment and are central in determining growth cone shape and the rate and direction of advance. In support of this view, we show that PMA treatment retards neurite sprouting, alters growth cone morphology and motility, and eliminates the appearance of microfilament bundles, filopodia, and FN-containing substratum-attachment plaques.
Actin Cytoskeleton↗
Laminin-like antigen in rat CNS neurons: distribution and changes upon brain injury and nerve growth factor treatment.
Using several antibodies against rat or human laminin and an avidin-biotin immunocytochemical protocol, laminin-like immunoreactivity was detectable in the rat nervous system in expected locations, i.e., associated with blood vessels and reactive astrocytes. However, laminin staining was also abundantly present within neuronal cell bodies in most parts of the developing and adult rat CNS. Medial septum neuronal immunoreactivity was lost after septo-hippocampal disconnection, but could be preserved or even restored by intraventricular administration of nerve growth factor. Thus, at least for medial septum neurons, this laminin-like molecule can be accumulated or produced independent of direct hippocampal (target) contact. It remains to be determined whether CNS neuronal "laminin" processes activities similar to those found for laminin in vitro.
Aging↗
Schwannoma cell-derived inhibitor of the neurite-promoting activity of laminin.
During the purification of laminin-proteoglycan complexes from rat RN22 Schwannoma cell-conditioned medium, a laminin-rich fraction was obtained which lacked neurite-promoting activity. Since laminin from several sources is known to have potent neurite-promoting activity, this result suggested that either this laminin was inactive or its activity was somehow masked by associated molecule(s). The latter possibility was supported by the demonstration that the inactive laminin-containing fraction inhibited active laminin-containing fractions. This inhibitory activity was partially purified by using ion exchange chromatography and isopycnic centrifugation. The purified material contained proteoglycan based on its high affinity for cationic resin, high buoyant density, large heterodisperse appearance on electrophoretic gels, ability to label with inorganic sulfate, sensitivity to trypsin and glycosaminoglycan lyases, and heat stability. A quantitative in vitro bioassay was used to monitor the inhibitor after treatments aimed at defining its activity. The isolated Schwannoma-derived inhibitor (a) inhibits the neurite-promoting activity of purified rat, mouse, and human laminin; (b) is active whether presented to laminin in solution or after either the inhibitor or laminin is first bound to the culture substratum; (c) does not act by displacing laminin from the substratum; (d) can be prevented from binding to neurite-promoting laminin substrates by polyclonal and monoclonal anti-laminin or polyclonal anti-entactin antibodies; and (e) is abolished by proteases or glycosaminoglycan lyases but not by heat. The above results suggest that the neurite-promoting activity of laminin is subject to regulation through association with a proteoglycan and entactin.
Animals↗
The effect of manipulating maternal behavior during an interaction on three- and six-month-olds' affect and attention.
3 studies were designed to examine the "still-face" paradigm, in which mothers stared at their 3- or 6-month-olds for a brief, still-face period interposed between 2 periods of normal face-to-face interaction. 6-month-olds decreased smiling and gazing at their mothers and grimaced more during the still-face period relative to the other periods; no period effects occurred in a no-change control group (Studies 1 and 2). Similar results were obtained when mothers and their infants observed and interacted with each other over closed-circuit color television monitors (Study 3). Moreover, the same relative decline in the infants' visual attention and positive affect during the still-face period occurred to a change in mothers' facial display (a televised, prerecorded, still face vs. a televised, live, interacting face) regardless of the presence or absence of their interactive voices (sound on the infants' monitor turned on or off). 3-month-olds exhibited a significant still-face effect, but only when maternal touch was a part of the manipulation (Study 1 vs. 2); therefore, the televised procedure was not conducted. The still-face effect is a robust phenomenon, produced with either "live" or "televised" procedures, both of which offer promising techniques for examining models of socioemotional perception/understanding of infants.
Affect↗
Acetate and fluoroacetate as possible markers for glial metabolism in vivo.
[3H]Acetate has been shown by light autoradiographic methods to label the neuropil but not the perikarya in brain and retina. [3H]Fluoroacetate behaves similarly. The study provides anatomical data which support the concept of metabolic compartmentation of glutamic acid and associated metabolites previously derived from biochemical studies. It is suggested that these may be markers of non-neuronal metabolism, probably mostly glial, and may be used to develop procedures which will provide complementary data to that obtained with 2-deoxyglucose on regional metabolism in brain.
Acetates↗