Alpha1beta1-integrin is an essential signal for neurite outgrowth induced by thrombospondin type 1 repeats of SCO-spondin.

In the central and peripheral nervous systems a heterogeneous group of proteins constituting the thrombospondin superfamily provides a cue for axonal pathfinding. They either contain or are devoid of the tripeptide RGD, and the sequence(s) and mechanism(s) which trigger in vitro their neurite-promoting activity have remained unclear. In this study, we reconsider the problem of whether sequences present in the thrombospondin type 1 repeats (TSRs), and independent of the well-known RGD-binding site, may activate integrins and account for their neurite-promoting activity. SCO-spondin is a newly identified member of the thrombospondin superfamily, which shows a multidomain organization with a great number of TSR motifs but no RGD sequence. Previous research has implicated oligopeptides derived from SCO-spondin TSRs in in-vitro development of various neuronal cell types. In this study, we investigate whether function-blocking antibodies directed against integrin subunits can block these effects in cell line B104, cloned from a neuroblastoma of the rat central nervous system. By two different approaches: flow cytometry revealing short-term effects and cell cultures revealing long-term effects, we show that: (a). activation of cell metabolism, (b). changes in cell size and structure, and (c). neurite-promoting activity induced by TSR oligopeptides are inhibited by function-blocking antibodies to beta1-subunit. Using a panel of function-blocking antibodies directed against various integrin alpha-subunits we show that the alpha1-subunit might be the partner of the beta1-subunit in B104 cells. Thus, we demonstrate that an original sequence within a TSR motif from SCO-spondin promotes neurite outgrowth through an intracellular signal driven by integrins, independently of an RGD-binding site.

Effects of SCO-spondin thrombospondin type 1 repeats (TSR) in comparison to Reissner's fiber material on the differentiation of the B104 neuroblastoma cell line.

SCO-spondin is a newly identified protein that is strongly expressed in the subcommissural organ (SCO), an ependymal differentiation of the brain. When released into the cerebrospinal fluid at the entrance to the Sylvian aqueduct, the glycoproteins condense and form a thread-like structure, Reissner's fiber (RF). To analyze the role of SCO-spondin on neuronal development, we studied the effects induced by an oligopeptide derived from a thrombospondin type 1 repeat (TSR) of SCO-spondin on neuroblastoma B104 cells and compared them with the effects of soluble RF material containing complete SCO-spondin proteins. In low density cell culture, the TSR peptide first induced a notable flattening of cells accompanied by increased neurite outgrowth. Grouping of these differentiated B104 cells, which later formed dense aggregates, was then observed with increasing time in culture. Soluble RF material induced similar morphological changes and neurite-promoting effects on B104 cells, although the cells remained evenly distributed throughout the culture time and no aggregates were visible. In high-density cell culture, both TSR peptide and RF material induced prominent neurite outgrowth and subsequent rapid cell aggregation. Whereas soluble RF material inhibited cell proliferation, no respective effect was observed in the presence of the TSR peptide. A direct interaction of TSR peptide and soluble RF material with a B104 cell binding site was revealed by increased B104 cell metabolic activity by flow cytometry.

Subcommissural organ/Reissner's fiber complex: characterization of SCO-spondin, a glycoprotein with potent activity on neurite outgrowth.

In the developing vertebrate nervous system, several proteins of the thrombospondin superfamily act on axonal pathfinding. By successive screening of a SCO-cDNA library, we have characterized a new member of this superfamily, which we call SCO-spondin. This extracellular matrix glycoprotein of 4,560 amino acids is expressed and secreted early in development by the subcommissural organ (SCO), an ependymal differentiation located in the roof of the Sylvian aqueduct. Furthermore, SCO-spondin makes part of Reissner's fiber (RF), a thread-like structure present in the central canal of the spinal cord. This novel protein shows a unique arrangement of several conserved domains, including 26 thrombospondin type 1 repeats (TSR), nine low-density lipoprotein receptor (LDLr) type A domains, two epidermal growth factor (EGF)-like domains, and N- and C-terminal von Willebrand factor (vWF) cysteine-rich domains, all of which are potent sites of protein-protein interaction. Regarding the huge number of TSR, the putative function of SCO-spondin on axonal guidance is discussed in comparison with other developmental molecules of the CNS exhibiting TSR. To correlate SCO-spondin molecular feature and function, we tested the effect of oligopeptides, whose sequences include highly conserved amino acids of the consensus domains on a neuroblastoma cell line B 104. One of these peptides (WSGWSSCSRSCG) markedly increased neurite outgrowth of B 104 cells and this effect was dose dependent. Thus, SCO-spondin is a favorable substrate for neurite outgrowth and may participate in the posterior commissure formation and spinal cord differentiation during ontogenesis of the central nervous system.

Identification of a multidrug resistance-like system in Tetrahymena pyriformis: evidence for a new detoxication mechanism in freshwater ciliates.

The freshwater ciliate Tetrahymena pyriformis is an ubiquitous organism that is present in all aquatic ecosystems. This protozoan showed a clear resistance against some polycyclic aromatic hydrocarbons which can be attributed to an efflux pump probably of the multidrug resistance (MDR) type. Immunocytochemical detection showed a positive stain of ciliate cells using the monoclonal antibodies 4E3, raised against P-glycoprotein (P-gp). The kinetics of P-gp expression were studied for control cultures and cultures treated with 15 microM benzo(a)pyrene. Western blot analysis using the Ab1, anti-P-gp polyclonal antibodies indicates the presence of two bands of 66 and 96 kDa of which the intensity increased with time in benzo(a)pyrene-treated ciliates. Uptake experiments with target compounds for the MDR pump, namely adriamycin, rhodamine 123 and two polycyclic aromatic hydrocarbons, benzo(a)pyrene and 7,12-dimethylbenzanthracene, were carried out by flow cytometry, in the presence or absence of cyclosporin (an inhibitor of the multidrug resistant pump). The data indicate that the accumulation of these compounds by ciliate cells is significantly enhanced in the presence of cyclosporin. This suggests that Tetrahymena is provided with a P-gp-like system that is functionally active in a way similar to that of the mammalian P-gp.

A multidisciplinary TBI inpatient rehabilitation programme for active duty service members as part of a randomized clinical trial.

OBJECTIVE: To design and describe an effective rehabilitation programme for use in an ongoing trial on the efficacy of multidisciplinary brain injury rehabilitation for moderately head injury military service members. DESIGN: Treatment arm of a randomized control trial. SETTING: US military tertiary care hospital inpatient rehabilitation programme. PATIENTS: Sixty seven active duty military with moderate to severe TBI who were randomized to the treatment arm of the protocol. INTERVENTION: Eight week rehabilitation programme combining group and individual therapies with an inpatient milieu-oriented neuropsychological focus. Group therapies included fitness, planning and organization, cognitive skills, work skills, medication, and milieu groups, and community re-entry outings. Individual therapy included neuropsychology, work therapy, occupational therapy, and speech and language pathology. MAIN OUTCOME MEASURES: Successful return to work and return to duty. RESULTS: At 1 year follow-up, 64 patients returned to work (96%) and 66% (44/67) returned to duty. CONCLUSION: The described rehabilitation programme demonstrates one successful effort to rehabilitate active duty military service members with TBI who have the potential to return to duty.

Uptake and efflux of polycyclic aromatic hydrocarbons by Tetrahymena pyriformis: evidence for a resistance mechanism.

The action of benzo(a)pyrene (BP), 3-methylcholanthrene (3MC), benzanthracene (BA), and 7,12-dimethylbenzanthracene (DMBA), four polycyclic aromatic hydrocarbons (PAHs), was studied on the unicellular protozoan Tetrahymena pyriformis. This ciliate was exposed to the PAHs at 1, 15, and 37 microM for up to 6 h. BP and BA caused a slight inhibition of cell growth, whereas 3MC and DMBA showed no detectable effect. Cell viability remained unaffected by the PAHs at all concentrations and exposure times tested. Cellular accumulation of PAHs was studied using flow cytometry. The results show immediate accumulation followed by rapid elimination of the compounds. BP uptake was also studied in the presence of verapamil and cyclosporin, compounds known as inhibitors of the multidrug resistance (MDR) pump. In the presence of verapamil, BP was accumulated in larger amounts in cells. With cyclosporin, the accumulation of the PAH was several times higher than under control conditions. The results of GC/MS analysis show that PAH elimination was not linked to biotransformation. These results suggest that the resistance of Tetrahymena against PAH cytotoxicity may be attributed to the rapid efflux of these agents from the cells via an efflux pump probably of the MDR type.

Epinigericin toxicity towards Tetrahymena pyriformis GL; changes in cell volume and intracellular pH.

A study of the toxicity of epinigericin, an antibiotic ionophor, towards the ciliate Tetrahymena pyriformis showed that this molecule stopped cell division, increased cell volume and led to a more basic intracellular pH. The action of epinigericin was probably linked to its function as an ionophor. The ionic selectivity of this molecule is still not known. The raising of the intracellular pH of ciliates by this antibiotic may be linked to its toxic action and its iontransport mechanism in Tetrahymena.

Change in intracellular pH in Tetrahymena pyriformis GL in relation to the toxicity level of the lonophorous antibiotic nigericin.

Nigericin, a carboxylic poly ether antibiotic, is toxic towards Tetrahymena pyriformis GL [1, 7, 12, 13]. Nigericin transports K(+) across biological membranes along the gradient. This transport is generally equilibrated by an influx of H(+) ions. The toxicity of nigericin (at low 10 mg · l(-1) and high 30 mg · l(-1) levels) was studied by measuring the intracellular pH of Tetrahymena pyriformis GL by means of two labelled molecules: (14)C-DMO and (3)H-inulin. This measurement of pHi requires prior knowledge of the number of cells and their volume. The results reveal a correlation of the toxicity of nigericin, acidification of the intracellular environment and increase in cell volume leading to the return of pHi to control values.

Microbial conversion of lonophorous antibiotic nigericin by the ciliate Tetrahymena pyriformis.

The ionophorous antibiotic nigericin is toxic towards the ciliate Tetrahymena pyriformis GL. At the high concentration of 30 mg/l (sublethal dose), it is bioconverted into several products. The yield of one of these (N1) is appreciably improved with pretreated cells, higher concentrations of nigericin (50 or 100 mg/1), and the presence of a larger ciliate biomass. A structural study of N1 by FAB mass spectrometry combined with tandem mass spectrometry and nuclear magnetic resonance shows it to be an epimer, epinigericin, about half as toxic as nigericin. Bioconversion of nigericin by T. pyriformis may be regarded as a detoxication process.