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At least 1,063 records · Page 59Linked to original sources
PubMed2006

Anthrax toxin receptor 1/tumor endothelium marker 8 mediates cell spreading by coupling extracellular ligands to the actin cytoskeleton.

Tumor endothelial marker 8 (TEM8) is induced in tumor-associated vasculature and acts as a receptor for Protective Antigen (PA), the cell-binding component of the anthrax toxin determinant for toxin entrance into cells. However, the normal function for TEM8 remains unknown. We show that TEM8 functions as an adhesion molecule mediating cell spreading on immobilized PA and collagen I. The mechanism for TEM8 interaction with collagen I was cell type-specific, because binding to collagen I was abrogated by beta1 integrin function blocking antibody in HEK293 cells, but not in primary synovial rabbit fibroblasts. Binding to PA remained unaffected by the addition of beta1 integrin function blocking antibody. Whereas the extracellular and transmembrane domains of TEM8 were sufficient to provide cell attachment, the intracellular domain was critical for spreading. Fusion of the cytosolic domain of TEM8 to the IL-2 receptor, conferred cell-spreading capability on IL-2 receptor antibody substrates. The cytoplasmic domain mediated linkage with the actin cytoskeleton as it co-precipitated actin and determined partitioning of TEM8 to the actin-containing detergent insoluble cellular fraction. TEM8 anchorage to actin was relevant as spreading was inhibited by the cytoskeleton-disrupting drug cytochalasin D, but persisted in the presence of the microtubule-depolymerizing drug nocodazole, and in cells lacking intermediate filaments. Thus, our results indicate that TEM8 is a new adhesion molecule linking collagen I or PA to the actin cytoskeleton.

Actins↗
PubMed2006

Laminin alpha1 chain LG4 module promotes cell attachment through syndecans and cell spreading through integrin alpha2beta1.

The laminin alpha1 chain is a subunit of laminin-1, a heterotrimeric basement membrane protein. The LG4-5 module at the C terminus of laminin alpha1 contains major binding sites for heparin, sulfatide, and alpha-dystroglycan and plays a critical role in early embryonic development. We previously identified active synthetic peptides AG73 and EF-1 from the sequence of laminin alpha1 LG4 for binding to syndecan and integrin alpha2beta1, respectively. However, their activity and functional relationship within the laminin-1 and LG4 as well as the functional relation between these sites and alpha-dystroglycan binding sites in LG4 are not clear. To address these questions, we created mutant recombinant LG4 proteins containing alanine substitutions within the AG73 (M1), EF-1 (M2, M3), and alpha-dystroglycan binding sites (M4, M5) and analyzed their activities. We found that recombinant proteins rec-M1 and rec-M5, containing mutations within M1 and M5, respectively, did not bind heparin or lymphoid cell lines expressing syndecans. These results suggest that LG4 binds to heparin and syndecans through M1 and M5. Rec-M1 and rec-M5 reduced fibroblast attachment, whereas mutant rec-M2 and rec-M3 retained cell attachment activity but did not promote cell spreading. Fibroblast attachment to rec-LG4 was inhibited by heparin but not by integrin antibodies. Spreading of fibroblasts on rec-LG4 was inhibited by anti-integrin alpha2 and beta1 but not by anti-integrin alpha1 and alpha6. These results suggest that the M1 and M5 sites are necessary for cell attachment on LG4 through syndecans and that the EF-1 site is for cell spreading activity through integrin alpha2beta1. In contrast, laminin-1-mediated fibroblast attachment and spreading were not inhibited by heparin or anti-integrin alpha2. Our findings indicate that LG4 has a unique function distinct from laminin-1 and suggest that laminin alpha1 LG4-5 may also be produced by a proteolytic cleavage in certain tissues where it exerts its activity.

Alanine↗
PubMed2006

Identification of the heparin-binding determinants within fibronectin repeat III1: role in cell spreading and growth.

Fibronectins are high molecular mass glycoproteins that circulate as soluble molecules in the blood, and are also found in an insoluble, multimeric form in extracellular matrices throughout the body. Soluble fibronectins are polymerized into insoluble extracellular matrix (ECM) fibrils via a cell-dependent process. Recent studies indicate that the interaction of cells with the ECM form of fibronectin promotes actin organization and cell contractility, increases cell growth and migration, and enhances the tensile strength of artificial tissue constructs; ligation of integrins alone is insufficient to trigger these responses. Evidence suggests that the effect of ECM fibronectin on cell function is mediated in part by a matricryptic heparin-binding site within the first III1 repeat (FNIII1). In this study, we localized the heparin-binding activity of FNIII1 to a cluster of basic amino acids, Arg613, Trp614, Arg615, and Lys617. Site-directed mutagenesis of a recombinant fibronectin construct engineered to mimic the ECM form of fibronectin demonstrates that these residues are also critical for stimulating cell spreading and increasing cell proliferation. Cell proliferation has been tightly correlated with cell area. Using integrin- and heparin-binding fibronectin mutants, we found a positive correlation between cell spreading and growth when cells were submaximally spread on ECM protein-coated surfaces at the time of treatment. However, cells maximally spread on vitronectin or fibronectin still responded to the fibronectin matrix mimetic with an increase in growth, indicating that an absolute change in cell area is not required for the increase in cell proliferation induced by the matricryptic site of FNIII1.

Amino Acid Motifs↗
PubMed2004

Spatial spread of neural excitation: comparison of compound action potential and forward-masking data in cochlear implant recipients.

The feasibility of using the electrically evoked compound action potential (ECAP), measured with the NRT system (Neural Response Telemetry) and the NRT software (version 2.04), to quantify the longitudinal spread of neural excitation was examined in four subjects fitted with the Nucleus C124M cochlear implant. The ECAP and psychophysical forward-masking profiles were measured using stimulation on each of three electrodes, in basal, middle and apical positions. Spatial spread profiles derived from the ECAP measure produced broader functions than those derived from the psychophysical measure. These results, together with investigation of the change of ECAP spread pattern with stimulation current, suggest that functions derived from this 'simple' method were more influenced by the spread of electric field from excited neuron to electrode array than by breadth of the neural excitation pattern. The recently released NRT version 3.0 permits the masker and probe pulses to be delivered to separate electrodes, thus removing a fundamental limitation of version 2.04. Results from a pilot study, in which this capability was exploited, suggest that the spatial functions from this 'advanced' method may provide a better correlation with results from psychophysical forward masking.

Action Potentials↗
PubMed2002

The effects of surfactants on adhesion, spreading, and retention of herbicide droplet on the surface of the leaves and seeds.

Droplet adhesion, spreading, and retention on leaf and seed surfaces are studied in the presence of surfactants for successful formulation of a herbicide whereby efficient coverage, less wastage, and environment protection are achieved. Cationic, anionic, and nonionic surfactants, e.g., HTAB, SDBS, and tergitol, were added to water and the static contact angle of water droplet was measured on cauliflower, cabbage, spinach leaves, French bean, wheat, and Bengal gram seeds. Droplet adhesion, spreading, and retention were analysed in terms of static contact angle and physical properties of the system. The presence of a small quantity (0.1 wt.%) of tergitol in water increased the adhesion, spreading, and retention of droplet on all leaf and seed surfaces tested. Tergitol, a nonionic surfactant, is likely to be adsorbed more than the ionic surfactants HTAB and SDBS at the water/leaf (or seed)/air interface since plant leaves and seeds are nonionic in nature. The addition of 0.1% wt. of tergitol to a common herbicide, derosal, increases the adhesion, spreading, and retention of derosal on leaf and seed surfaces, consequently, efficient coverage and minimum wastage are attained.

Adhesiveness↗
PubMed1986

Binding and spreading of hepatocytes on synthetic galactose culture surfaces occur as distinct and separable threshold responses.

Isolated rat hepatocytes bind to synthetic flat polyacrylamide matrices containing covalently attached galactose residues in a sugar-specific and concentration-dependent manner. Cell binding is mediated by the asialoglycoprotein receptor and occurs as a threshold response at or above a critical concentration of sugar in the matrix. Hepatocytes in the presence or absence of serum were able to spread on these synthetic galactose surfaces and were morphologically similar to cells on tissue culture plastic. Cell spreading also occurred as a threshold response but at a much higher critical concentration of sugar than for the cell-binding response. Above the critical concentration for spreading, the area occupied by a cell increased as the sugar concentration increased. By manipulating the galactose content of the matrix, cell spreading and cell binding can be differentiated as independent and separable threshold responses to the extracellular substratum.

Acrylic Resins↗
PubMed1989

Actin filaments and the growth, movement, and spread of the intracellular bacterial parasite, Listeria monocytogenes.

Listeria monocytogenes was used as a model intracellular parasite to study stages in the entry, growth, movement, and spread of bacteria in a macrophage cell line. The first step in infection is phagocytosis of the Listeria, followed by the dissolution of the membrane surrounding the phagosome presumably mediated by hemolysin secreted by Listeria as nonhemolytic mutants remain in intact vacuoles. Within 2 h after infection, each now cytoplasmic Listeria becomes encapsulated by actin filaments, identified as such by decoration of the actin filaments with subfragment 1 of myosin. These filaments are very short. The Listeria grow and divide and the actin filaments rearrange to form a long tail (often 5 microns in length) extending from only one end of the bacterium, a "comet's tail," in which the actin filaments appear randomly oriented. The Listeria "comet" moves to the cell surface with its tail oriented towards the cell center and becomes incorporated into a cell extension with the Listeria at the tip of the process and its tail trailing into the cytoplasm behind it. This extension contacts a neighboring macrophage that phagocytoses the extension of the first macrophage. Thus, within the cytoplasm of the second macrophage is a Listeria with its actin tail surrounded by a membrane that in turn is surrounded by the phagosome membrane of the new host. Both these membranes are then solubilized by the Listeria and the cycle is repeated. Thus, once inside a host cell, the infecting Listeria and their progeny can spread from cell to cell by remaining intracellular and thus bypass the humoral immune system of the organism. To establish if actin filaments are essential for the spread of Listeria from cell to cell, we treated infected macrophages with cytochalasin D. The Listeria not only failed to spread, but most were found deep within the cytoplasm, rather than near the periphery of the cell. Thin sections revealed that the net of actin filaments is not formed nor is a "comet" tail produced.

Actin Cytoskeleton↗
PubMed1993

Phosphorylation-site mutagenesis of the growth-associated protein GAP-43 modulates its effects on cell spreading and morphology.

The 43-kD growth-associated protein (GAP-43) is a major protein kinase C (PKC) substrate of axonal growth cones, developing nerve terminals, regenerating axons, and adult central nervous system areas associated with plasticity. It is a cytosolic protein associated with the cortical cytoskeleton and the plasmalemma. Membrane association of GAP-43 is mediated by palmitoylation at Cys3Cys4. In vitro and in vivo, phosphorylation by PKC exclusively involves Ser41 of mammalian GAP-43 (corresponding to Ser42 in the chick protein). To identify aspects of GAP-43 function, we analyzed the actions of wild-type, membrane-association, and phosphorylation-site mutants of GAP-43 in nonneuronal cell lines. The GAP-43 constructs were introduced in L6 and COS-7 cells by transient transfection. Like the endogenous protein in neurons and their growth cones, GAP-43 in nonneuronal cells associated with the cell periphery. GAP-43 accumulated in the pseudopods of spreading cells and appeared to interact with cortical actin-containing filaments. Spreading L6 cells expressing high levels of recombinant protein displayed a characteristic F-actin labeling pattern consisting of prominent radial arrays of peripheral actin filaments. GAP-43 had dramatic effects on local surface morphology. Characteristic features of GAP-43-expressing cells were irregular cell outlines with prominent and numerous filopodia. The effects of GAP-43 on cell morphology required association with the cell membrane, since GAP-43(Ala3Ala4), a mutant that failed to associate with the cell cortex, had no morphogenetic activity. Two GAP-43 phosphorylation mutants (Ser42 to Ala42 preventing and Ser42 to Asp42 mimicking phosphorylation by PKC) modulated the effects of GAP-43 in opposite ways. Cells expressing GAP-43(Asp42) spread extensively and displayed large and irregular membranous extensions with little filopodia, whereas GAP-43(Ala42) produced small, poorly spreading cells with numerous short filopodia. Therefore, GAP-43 influences cell surface behavior and phosphorylation modulates its activity. The presence of GAP-43 in growing axons and developing nerve termini may affect the behavior of their actin-containing cortical cytoskeleton in a regulatable manner.

Actin Cytoskeleton↗
PubMed1993

Depletion of intracellular potassium disrupts coated pits and reversibly inhibits cell polarization during fibroblast spreading.

To learn more about the possible role of the coated pits endocytic pathway in cell adhesion, we studied attachment and spreading of fibroblasts whose coated pits were disrupted by depletion of intercellular potassium. Fibroblasts incubated in suspension in potassium-free medium lost 80% of their intracellular potassium within 10 min and showed disrupted coated pits based on fluorescence staining of clathrin. Potassium-depleted cells attached and spread on fibronectin-coated substrata over the same time course (15 min-2 h) as control cells. Unlike controls, however, potassium-depleted fibroblasts attained a radial morphology with circumferentially organized actin filament bundles and were unable to make the transition to a polarized morphology with stress fibers. In the radially spread fibroblasts, fibronectin receptors and vinculin colocalized in focal adhesion sites and appeared to be membrane insertion points for circumferentially arranged actin filament bundles, but these sites were much smaller than the focal adhesion plaques in polarized cells. The effects of potassium depletion on cell adhesion were reversible. Within 1 h after switching K(+)-depleted fibroblasts to medium containing KCl, cells developed a polarized morphology with actin stress fibers inserting into focal adhesion plaques. Coated pits also reformed on the cell surface during this time. Because formation of focal adhesion plaques preceded reappearance of clathrin-coated pits at the cell margins, it seems unlikely that coated pits play a direct role in adhesion plaque assembly. Polarization of fibroblasts upon addition of KCl was inhibited by ouabain showing that intracellular potassium was required for activity. Polarization also was inhibited when potassium-depleted cells were switched to potassium-containing medium under hypertonic or acidified conditions, both of which have been shown to inhibit receptor-mediated endocytosis. Our results suggest that the coated pit endocytic pathway is not required for initial attachment, spreading, and formation of focal adhesions by fibroblasts, but may play a role in cell polarization.

Actins↗
PubMed1994

Syndecan-1 expressed in Schwann cells causes morphological transformation and cytoskeletal reorganization and associates with actin during cell spreading.

To investigate the biological functions of transmembrane proteoglycans we have produced clonal cell lines of rat Schwann cells that express the hybrid proteoglycan syndecan-1. This was done by transfection of newborn rat Schwann cells with a plasmid vector bearing the rat syndecan-1 cDNA sequence under transcriptional control of the constitutively active cytomegalovirus promoter, and a neomycin resistance gene. Stably expressing cells were selected by growth in G418. Expression of syndecan-1 was verified by Northern and immunoblot analysis and immunoprecipitation of 35SO4-labeled proteoglycans. The syndecan-1 expressing cells exhibited significantly enhanced spreading on several different substrata, including fibronectin and laminin, and an altered morphology. The enhanced spreading appeared to result from the presence of syndecan-1, based on the observation that anti-syndecan-1 antibodies inhibited the enhanced substratum spreading. There was also a reorganization of cytoskeletal structures and formation of focal adhesions, visualized by anti-vinculin staining, which were absent from control Schwann cells. There was no apparent stable association of cell surface syndecan-1 with focal contact sites, as determined by dual staining with anti-syndecan-1 and anti-vinculin antibodies. Colocalization of patches of cell surface syndecan-1 with actin was observed, but only during cell spreading. These findings provide evidence for a role of transmembrane proteoglycans in cellular morphogenesis, and suggest that transient association of syndecans with microfilaments may be an important aspect of their biological function.

Actins↗
PubMed1994

Single subunit chimeric integrins as mimics and inhibitors of endogenous integrin functions in receptor localization, cell spreading and migration, and matrix assembly.

The ability of single subunit chimeric receptors containing various integrin beta intracellular domains to mimic and/or inhibit endogenous integrin function was examined. Chimeric receptors consisting of the extracellular and transmembrane domains of the small subunit of the human interleukin-2 receptor connected to either the beta 1, beta 3, beta 3B, or beta 5 intracellular domain were transiently expressed in normal human fibroblasts. When expressed at relatively low levels, the beta 3 and beta 5 chimeras mimicked endogenous ligand-occupied integrins and, like the beta 1 chimera (LaFlamme, S. E., S. K. Akiyama, and K. M. Yamada. 1992. J. Cell Biol. 117:437), concentrated with endogenous integrins in focal adhesions and sites of fibronectin fibril formation. In contrast, the chimeric receptor containing the beta 3B intracellular domain (a beta 3 intracellular domain modified by alternative splicing) was expressed diffusely on the cell surface, indicating that alternative splicing can regulate integrin receptor distribution by an intracellular mechanism. Furthermore, when expressed at higher levels, the beta 1 and beta 3 chimeric receptors functioned as dominant negative mutants and inhibited endogenous integrin function in localization to fibronectin fibrils, fibronectin matrix assembly, cell spreading, and cell migration. The beta 5 chimera was a less effective inhibitor, and the beta 3B chimera and the reporter lacking an intracellular domain did not inhibit endogenous integrin function. Comparison of the relative levels of expression of the transfected beta 1 chimera and the endogenous beta 1 subunit indicated that in 10 to 15 h assays, the beta 1 chimera can inhibit cell spreading when expressed at levels approximately equal to the endogenous beta 1 subunit. Levels of chimeric receptor expression that inhibited cell spreading also inhibited cell migration, whereas lower levels were able to inhibit alpha 5 beta 1 localization to fibrils and matrix assembly. Our results indicate that single subunit chimeric integrins can mimic and/or inhibit endogenous integrin receptor function, presumably by interacting with cytoplasmic components critical for endogenous integrin function. Our results also demonstrate that beta intracellular domains, expressed in this context, display specificity in their abilities to mimic and inhibit endogenous integrin function. Furthermore, the approach that we have used permits the analysis of intracellular domain function in the processes of cell spreading, migration and extracellular matrix assembly independent of effects due to the rest of integrin dimers. This approach should prove valuable in the further analysis of integrin intracellular domain function in these and other integrin-mediated processes requiring the interaction of integrins with cytoplasmic components.

Amino Acid Sequence↗
PubMed2001

The LD4 motif of paxillin regulates cell spreading and motility through an interaction with paxillin kinase linker (PKL).

The small GTPases of the Rho family are intimately involved in integrin-mediated changes in the actin cytoskeleton that accompany cell spreading and motility. The exact means by which the Rho family members elicit these changes is unclear. Here, we demonstrate that the interaction of paxillin via its LD4 motif with the putative ARF-GAP paxillin kinase linker (PKL) (Turner et al., 1999), is critically involved in the regulation of Rac-dependent changes in the actin cytoskeleton that accompany cell spreading and motility. Overexpression of a paxillin LD4 deletion mutant (paxillinDeltaLD4) in CHO.K1 fibroblasts caused the generation of multiple broad lamellipodia. These morphological changes were accompanied by an increase in cell protrusiveness and random motility, which correlated with prolonged activation of Rac. In contrast, directional motility was inhibited. These alterations in morphology and motility were dependent on a paxillin-PKL interaction. In cells overexpressing paxillinDeltaLD4 mutants, PKL localization to focal contacts was disrupted, whereas that of focal adhesion kinase (FAK) and vinculin was not. In addition, FAK activity during spreading was not compromised by deletion of the paxillin LD4 motif. Furthermore, overexpression of PKL mutants lacking the paxillin-binding site (PKLDeltaPBS2) induced phenotypic changes reminiscent of paxillinDeltaLD4 mutant cells. These data suggest that the paxillin association with PKL is essential for normal integrin-mediated cell spreading, and locomotion and that this interaction is necessary for the regulation of Rac activity during these events.

ADP-Ribosylation Factors↗
PubMed2004

c-Abl phosphorylates Dok1 to promote filopodia during cell spreading.

Filopodia are dynamic F-actin structures that cells use to explore their environment. c-Abl tyrosine kinase promotes filopodia during cell spreading through an unknown mechanism that does not require Cdc42 activity. Using an unbiased approach, we identified Dok1 as a specific c-Abl substrate in spreading fibroblasts. When activated by cell adhesion, c-Abl phosphorylates Y361 of Dok1, promoting its association with the Src homology 2 domain (SH2)/SH3 adaptor protein Nck. Each signaling component was critical for filopodia formation during cell spreading, as evidenced by the finding that mouse fibroblasts lacking c-Abl, Dok1, or Nck had fewer filopodia than cells reexpressing the product of the disrupted gene. Dok1 and c-Abl stimulated filopodia in a mutually interdependent manner, indicating that they function in the same signaling pathway. Dok1 and c-Abl were both detected in filopodia of spreading cells, and therefore may act locally to modulate actin. Our data suggest a novel pathway by which c-Abl transduces signals to the actin cytoskeleton through phosphorylating Dok1 Y361 and recruiting Nck.

Actins↗
PubMed2004

Phosphorylation of actopaxin regulates cell spreading and migration.

Actopaxin is an actin and paxillin binding protein that localizes to focal adhesions. It regulates cell spreading and is phosphorylated during mitosis. Herein, we identify a role for actopaxin phosphorylation in cell spreading and migration. Stable clones of U2OS cells expressing actopaxin wild-type (WT), nonphosphorylatable, and phosphomimetic mutants were developed to evaluate actopaxin function. All proteins targeted to focal adhesions, however the nonphosphorylatable mutant inhibited spreading whereas the phosphomimetic mutant cells spread more efficiently than WT cells. Endogenous and WT actopaxin, but not the nonphosphorylatable mutant, were phosphorylated in vivo during cell adhesion/spreading. Expression of the nonphosphorylatable actopaxin mutant significantly reduced cell migration, whereas expression of the phosphomimetic increased cell migration in scrape wound and Boyden chamber migration assays. In vitro kinase assays demonstrate that extracellular signal-regulated protein kinase phosphorylates actopaxin, and treatment of U2OS cells with the MEK1 inhibitor UO126 inhibited adhesion-induced phosphorylation of actopaxin and also inhibited cell migration.

Actinin↗
PubMed1976

Filopodia of spreading 3T3 cells. Do they have a substrate-exploring function?

Freshly plated 3T3 cells send out radial projections or filopodia. We observed cells which happended to settle on glass near the borderline of a gold-plated area. When some of the filopodia contacted the gold-plated area and others the glass substratum and remained attached for a few minutes, lamellipodia then extended preferentially toward the gold-plated area. 1-2 h later, most of the cells were found in the gold-plated area. When the filopodia of a spreading 3T3 cell contacted another already spread 3T3 cell and also the glass substratum, the first lamellipodia extended preferentially towards the glass. These observations suggest a directionally differentiated extension of lamellipodia after the filopodia of a spreading 3T3 cell have contacted different substrates in their environment. Before filopodia contact a substrate, they perform a rapid "scanning" motion. Therefore, we suggest that the filopodia of a spreading 3T3 cell serve as organs which explore the nonfluid environment and react to a certain quality of the substrate that is presently unknown. Subsequently, they mediate the extension of lamellipodia into the direction in which this quality is found. The described phenomena are reversibly inhibited by Cytochalasin B at concentrations above 5 mug/ml although filopodia are produced.

Cell Adhesion↗
PubMed1984

Myosin rings and spreading in mouse blastomeres.

The relationship between myosin organization and cell spreading in the preimplantation mouse embryo was studied by indirect immunofluorescence in embryos cultured on lectin-coated substrates. Binding of cell surface polysaccharides to substrate-bound concanavalin A and wheat germ agglutinin induced changes in myosin distribution that resembled those which occur during cell-cell contact interaction. This involved an initial loss of myosin from the contact region that was associated with the development of stable cell-substrate attachments. In addition, a ring of myosin was formed along the edge of the cells' contact to the substrate. The presence of such a ring may be related to the potential for subsequent cell spreading. A myosin ring was also identified in the apical junctional region of the outer morula cells where it similarly separated the cell periphery into contacted and free peripheral domains. Following these changes in myosin organization the embryos spread on the substrate by extension of lamellipodia. These movements were coupled to the dissolution of the myosin ring and the reorganization of myosin into filament bundles. The sequence of changes in the pattern of myosin distribution suggests that contact regulation of myosin organization plays an important role in controlling the spreading behavior of blastomeres and perhaps more generally in the organization of cells into epithelia.

Animals↗
PubMed1990

Effect of olfactory bulb ablation on spread of a neurotropic coronavirus into the mouse brain.

Previous results suggested that, after intranasal inoculation, mouse hepatitis virus (MHV), a neurotropic coronavirus, entered the central nervous system (CNS) via the olfactory and trigeminal nerves. To prove this hypothesis, the effect of interruption of the olfactory pathway on spread of the virus was studied using in situ hybridization. Unilateral surgical ablation of this pathway prevented spread of the virus via the olfactory tract on the side of the lesion. MHV RNA could be detected, however, at distal sites on the operated side, indicating that the virus spread via well-described circuits involving the anterior commissure from the control (intact) side of the brain. Viral transport via the trigeminal nerve was not affected by removal of the olfactory bulb, showing that the surgical procedure was specific for the olfactory pathway. These results prove conclusively that MHV gains entry to the CNS via a transneuronal route, and spreads to additional sites in the brain via known neuroanatomic pathways.

Animals↗
PubMed1950

Studies on entry and egress of poliomyelitis infection. II. Entry and spread after exposure of the trigeminal nerve.

Direct exposure to poliomyelitis virus of the central end of a cut branch of the V cranial nerve was followed by centripetal spread of infection to the semilunar (Gasserian) ganglion, involvement of which was detected both histologically and by subinoculation as early as the 3rd day. In some instances infection did not progress further; in others it spread into the CNS with initial involvement of the trigeminal centers in the pons and medulla as early as the 4th day and by the 5th day was further advanced but still limited to the brainstem. Once infection was established it progressed both rostrally and caudally, at times with great rapidity, through the brainstem and reached the cord on the 6th or a later day. Incidental exposure in traumatized muscle of peripheral fibers of the VII motor nerve led in some instances to spread along that pathway directly into the CNS. Application of the experimental results to human poliomyelitis is of interest chiefly in four respects. (1) The ascent of infection from a peripheral ganglion of the head area to the CNS with initial encephalitis of the brainstem and subsequent descent to the spinal cord is believed to parallel the evolution of the human disease as suggested by the character and order of development of the early symptoms and signs. (2) The failure in some instances of infection to spread from an infected peripheral ganglion to the CNS may parallel inapparent ("subclinical") poliomyelitis in man. (3) Invasion of virus through traumatized muscle directly to the CNS also has possible analogues in human experience which will be discussed in a later paper. (4) The presence of well marked and sometimes extensive lesions in the brainstem one or more days before symptoms emerge is also believed to parallel the human case.

Encephalitis↗