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Biomedical subjects

H Rösner

Publications and source records attributed to H Rösner.

At least 19 recordsLinked to original sources
PubMed2006

Effects of altered gravity on the actin and microtubule cytoskeleton of human SH-SY5Y neuroblastoma cells.

Human SH-SY5Y neuroblastoma cells were used to study the effects of altered gravity on the actin and microtubule cytoskeleton dynamics. A cholinergic stimulation of the cells during a 6 min period of changing gravity (3 parabolas) resulted in an enhanced actin-driven protrusion of evoked lamellipodia. Likewise, the spontaneous protrusive activity of nonactivated cells was promoted during exposure to changing gravity (6 up to 31 parabolas). Ground-based experiments revealed a similar enhancement of the spontaneous and evoked lamellar protrusive activity when the cells were kept at 2 g hypergravity for at least 6 min. This gravity response was independent of the direction of the acceleration vector in respect to the cells. Exposure of the cells to "simulated weightlessness" (clinorotation) had no obvious influence on this type of lamellar actin cytoskeleton dynamics. A 20 min exposure of the cells to simulated weightlessness or to changing gravity (6 to 31 parabolas) - but not to 2 g (hypergravity, centrifugation) - resulted in an altered arrangement of microtubules indicated by bending, turning, and loop formation. A similar altered arrangement was shown by microtubules which had polymerized into lamellipodia after release from a taxol block at simulated weightlessness (clinorotation) or during changing gravity (5 parabolas). Our data suggest that in human SH-SY5Y neuroblastoma cells, microgravity affects the dynamics and spatial arrangement of microtubules but has no influence on the Rac-controlled lamellar actin cytoskeleton dynamics and cell spreading. The latter, however, seems to be promoted at hypergravity.

Acetylcholine↗
PubMed2006

Volume change during the formation of nanoporous gold by dealloying.

We report a macroscopic shrinkage by up to 30 vol % during electrochemical dealloying of Ag-Au. Since the original crystal lattice is maintained during the process, we suggest that the formation of nanoporous gold in our experiments is accompanied by the creation of a large number of lattice defects and by local plastic deformation.

Journal Article↗
PubMed2006

[Tissue engineering of peripheral nerves].

BACKGROUND: In spite of considerable progress in microsurgical techniques, the treatment of long distance defects in peripheral nerves remains challenging for the surgeon. Autologous nerve grafting has been the only applicable procedure to overcome such defects in the past. Due to the known disadvantages of this procedure (neuroma formation and sensory deficits at the donor-site, limited availability of donor-material, etc.) and impaired regenerative results, different tubulisation techniques are discussed more frequently as alternatives to the autologous nerve grafts. AIM OF THE STUDY: In this work, the authors summarise their experiences and results with different synthetically developed materials, cellular and acellular tubes and venous conduits for the reconstruction of peripheral nerve defects. MATERIAL AND METHODS: To analyse peripheral nerve regeneration, we utilised a median nerve model in rats. In these studies nerve gaps up to 40 mm were induced. Guiding tubes of various materials (trimethylene carbonate-epsilon-caprolactone, polyethylene, veins, and collagen) were employed. Furthermore, we introduced Schwann cells as cellular elements into some of the trimethylene carbonate-epsilon-caprolactone tubes. The longest postoperative observation period was nine months. RESULTS: The results demonstrated that only in the case of cellular filled tubes (syngenic Schwann cells) did regeneration occur across the 20 mm gap. This regeneration was comparable to that induced after autologous grafting. Across a 40 mm gap the autologous graft demonstrated the best results.

Animals↗
PubMed2004

In vitro anti-proliferation/cytotoxic activity of sixty natural products on the human SH-SY5Y neuroblastoma cells with specific reference to dibenzyl trisulphide.

Sixty natural products belonging to the following structural classes: artemisinins, coumarins, flavonoids, tannins, tetrahydroberberine alkaloids, tetracyclic triterpenes, tetranortriterpenoids and polysulphides were screened against the human SH-SY5Y neuroblastoma cell line revealing differences in their effects on cell morphology and in anti-proliferation/cytotoxic activity. Based on the data obtained, dibenzyl trisulphide is the most effective anti-proliferative/cytotoxic compound. In addition, we hereby propose the human SH-SY5Y cell line as a sensitive and uncomplicated in vitro test system for detecting compounds with potential anti-proliferation/cytotoxic activity.

Antineoplastic Agents↗
PubMed2003

In vitro anti-proliferation/cytotoxic activity of cantharidin (Spanish Fly) and related derivatives.

The anti-cancer therapeutic promise of cantharidin is limited because of its high mammalian toxicity. In order to find new anti-cancer lead compounds with reduced toxicity of the cantharidin prototype, the following seven derivatives were screened against the human SH-SY5Y neuroblastoma and MCF-7 breast cancer cells in vitro: 2,3-dimethyl-7-oxabicylo-[2.2.1]heptane-2,3-dicarboxylic anhydride (cantharidin) [1], 1-cyclohexen-1,2-dicarboxylic anhydride [2], cis-4-cyclohexen-1,2-dicarboxylic anhydride [3], cis-1, 2-cyclohexanedicarboxylic anhydride [4], exo-7-oxabicyclo[2.2.1]hept-5-ene-2-3 dicarboxylic anhydride [5], exo-7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic anhydride (norcantharidin) [6], and (S)-(-)-O-acetylmalic anhydride [7]. Cantharidin, was found to be the most effective anti-proliferative compound on both cell lines. However, on the human neuroblastoma cells cantharidin was of equal toxicity to compound [6]. Mode of action studies revealed that cantharidin inhibited growth factor-mediated activation of mitogen activated protein kinase (MAPkinase) and attenuated the de-phosphorylation of the extracellular regulated kinases 1 and 2 (erk1 and erk2).

Anhydrides↗
PubMed2001

Disassembly of microtubules and inhibition of neurite outgrowth, neuroblastoma cell proliferation, and MAP kinase tyrosine dephosphorylation by dibenzyl trisulphide.

Dibenzyl trisulphide (DTS), a main lipophilic compound in Petiveria alliacea L. (Phytolaccaceae), was identified as one of the active immunomodulatory compounds in extracts of the plant. To learn more about its biological activities and molecular mechanisms, we conducted one-dimensional NMR interaction studies with bovine serum albumin (BSA) and tested DTS and related compounds in two well-established neuronal cell-and-tissue culture systems. We found that DTS preferentially binds to an aromatic region of BSA which is rich in tyrosyl residues. In SH-SY5Y neuroblastoma cells, DTS attenuates the dephosphorylation of tyrosyl residues of MAP kinase (erk1/erk2). In the same neuroblastoma cell line and in Wistar 38 human lung fibroblasts, DTS causes a reversible disassembly of microtubules, but it did not affect actin dynamics. Probably due to the disruption of the microtubule dynamics, DTS also inhibits neuroblastoma cell proliferation and neurite outgrowth from spinal cord explants. Related dibenzyl compounds with none, one, or two sulphur atoms were found to be significantly less effective. These data confirmed that the natural compound DTS has a diverse spectrum of biological properties, including cytostatic and neurotoxic actions in addition to immunomodulatory activities.

Animals↗
PubMed1999

1,2-dioctanoyl-s,n-glycerol-induced activation of protein kinase C results in striking, but reversible growth cone shape changes and an accumulation of f-actin and serine 41-phosphorylated GAP-43 in the axonal process.

In spinal cord explant cultures from embryonic chicken (E7) we found that both a long-time downregulation of PKC by phorbol-12,13-dibutyrate (PDBu) and an inhibition of PKC by RO-31-8220 strongly reduce neurite outgrowth. Unlike this, in the presence of a high dose of 1,2-dioctanoyl-s,n-glycerol (diC8, 60 microM), PKCalpha,beta isoforms are not downregulated, but neurite outgrowth appeared reduced up to 37 %. A low dose of diC8 (5 microM), however, was found to stimulate neurite outgrowth up to 25 %. Using this tissue culture system as well as neuronal cell culture we then studied the effects of diC8 on the shapes and actin-based motility of distal axonal processes and growth cones as well as on the spatial distribution of f-actin and serine 41-phosphorylated GAP-43 (neuromodulin, B50). High-resolution microscopy showed that addition of 30-60 microM diC8 leads within a few minutes to a retraction of filopodia and to an increased protrusion of lamellipodia followed by the formation of club-shaped dense growing tips, axonal varicosities, and a cessation of any actin dynamics. These striking shape changes are completely reversed after replacement of the medium by drug-free medium. Presence of cytochalasins and a panel of different PKC inhibitors prevent or respectively attenuate the diC8 effects. Immuno- and phalloidin-staining confirmed that in control neurons f-actin and serine 41-phosphorylated GAP-43 are confined to and enriched in the growth cones. In parallel with diC8-induced shape changes there is an accretion of f-actin and serine 41-phosphorylated GAP-43 in the entire axonal processes and the rounded growing tips. With respect to the fundamental role of the actin dynamics in growth cone steering and neuronal pathfinding, the data supports the view that in neurons local PKC-regulated phosphorylation of GAP-43 may represent an important mechanism to transduce guiding signals into actincytoskeletal responses mediating directed axonal growth.

Actins↗
PubMed1998

Significance of gangliosides in neuronal differentiation of neuroblastoma cells and neurite growth in tissue culture.

Addition of DL-threo-1-phenyl-2-decanolylamine-3-morpholino-1-propanol HCl (PDMP; 7-24 microM) or Fumonisin B1 (FB1; 30-50 microM) to SH-SY5Ytrk-A human neuroblastoma cells results within 4 days in a 40% decrease of the ganglioside content and in a reduction of nerve-growth-factor (NGF)-induced outgrowth of neuritic processes. NGF-induced enhancement of GAP-43 expression was not affected. However, unlike controls, immunostained GAP-43 appeared concentrated in defined areas of cell perikarya and mostly absent from cell processes. Presence of 20-microM exogenous GM1 for 4 days in NGF and PDMP containing cell cultures led to an increase of cell-associated GM1(15-fold), GM2 (10-fold), GM3 (15 fold), GD1a (4-fold), GD2, GD1b, and GT1b (all 3-fold), and partially reversed the PDMP (and FB1) effects on neurite growth and GAP-43 distribution. In a newly developed neuronal tissue culture system, PDMP and FB1 led to a comparable dose-dependent inhibition of neurite outgrowth from embryonic chicken spinal cord explants, which had been embedded into a fibrin matrix. In this system, addition of GM1 led to a further inhibition of neurite growth, probably due to an interaction with growth-promoting components present in the surrounding fibrin matrix.

Animals↗
PubMed1998

Polysialic acid on the neural cell adhesion molecule correlates with expression of polysialyltransferases and promotes neuroblastoma cell growth.

Neuroblastomas and cell lines derived from these tumors bear the oncodevelopmental antigen polysialic acid (PSA) bound to the neural cell adhesion molecule. Polysialyation of neural cell adhesion molecule can be achieved by two different polysialyltransferases, ST8SiaII and ST8SiaIV. This study was undertaken to investigate the pattern of polysialyltransferases expressed in the human neuroblastoma cell line SH-SY5Y. Reverse transcription-PCR showed simultaneous expression of the two enzymes, and in situ hybridization demonstrated that the polysialyltransferase mRNA expression parallels immunoreactivity with the PSA-specific monoclonal antibody 735. After retinoic acid-induced differentiation, only the PSA-positive, neuron-like cell type gave clear signals for ST8SiaII and ST8SiaIV in in situ hybridization, whereas both signals were drastically reduced in the weakly PSA-positive substrate adherent phenotype. Like the SH-SY5Y cells, a primary, PSA-positive neuroblastoma specimen revealed expression of the two polysialyltransferases. To investigate the role of PSA for cell growth and differentiation, SH-SY5Y cells were treated with the PSA-specific endo-N-acetylneuraminidase E. Although loss of PSA was accompanied with a marked reduction of cell growth, it did not interfere with retinoic acid-induced differentiation. Together, our results suggest that PSA surface expression is regulated on the level of polysialyltransferase transcription. Moreover, the similarity to the primary neuroblastoma tissue makes SH-SY5Y cells a suitable model system to examine further the role of polysialylation in tumor cell growth and the orchestration of PSA synthesis in neuroblastoma.

Cell Differentiation↗
PubMed1997

Organotypic spinal cord culture in serum-free fibrin gel: a new approach to study three-dimensional neurite outgrowth and of neurotoxicity testing: Effects of modulating the actin and tubulin dynamics and protein kinase activities.

Spinal cord explants from embryonic day seven (E7) chicken embryos were cultured without serum and in the presence of aprotinine, in a three-dimensional fibrin matrix. These conditions promote a robust, radial, unfasciculated outgrowth of neurites that are tipped by elaborate growth cones. Routinely after 5 days, the neurite outgrowth intensity (NOI) was determined by measuring the optical density of the immunostained neurites (image analysis program OPTIMAS version 5.2) within defined areas, extending radially for up to 3 mm from the explant border. A dose-dependent inhibition of NOI was determined for the cytoskeleton-affecting drugs nocodazole (half maximal inhibition ([I50]), 0.02 microM), taxol ([I50], 0.016 microM), cytochalasin D ([I50], 0.006 microM), and tetramethyl lead ([I50], 0.05 microM). Likewise, NOI was decreased in a dose-dependent fashion by ML-9 and RO-31-8220, inhibitors of myosin-light chain kinase and protein kinase C (PKC), respectively. The addition of 1,2-dioctanoyl-s,n-glycerol, a potent activator of PKC, led, at 5 microM, to an increase and at 30 and 60 microM to a decrease in NOI. The described system provides a rapid, reproducible, and quantitative assay for the effects of exogenous factors on the mode and intensity of neurite outgrowth.

Actins↗
PubMed1996

In growth cones of rat cerebral neurons and human neuroblastoma cells, activation of protein kinase C causes a shift from filopodial to lamellipodial actin dynamics.

In cultures of rat cerebral neurons addition of the protein kinase C (PKC) activator 1,2-dioctanoyl-s,n-glycerol (diC8; 5 microM) induces a transient elongation of filopodia which is followed by a striking enhancement of lamellar protrusions. After 30-40 min, lamellipodia are slowly retracted, filopodia reappear and become predominant again. The reappearance of filopodia is accelerated by addition of the potent PKC-inhibitor RO-31-8220 (2 microM). A similar transient promotion of lamellar protrusive activity is obtained in SH-SY5Y neuroblastoma cells upon stimulation by acetylcholine or diC8. Immunostainings showed that the new space created by extending actin-driven lamellipodia is rapidly entered by microtubules. Preincubation with or permanent presence of RO-31-8220 totally inhibits both filopodial and lamellipodial protrusive activity. The data suggest that both filopodial and lamellipodial protrusion require active PKC, however of different levels of activation.

Actins↗
PubMed1995

Complementary distribution of tau proteins in different phosphorylation states within growing axons.

Microtubule-associated tau proteins are hyperphosphorylated in brains from patients with Alzheimer's disease compared with normal adult human brain. At least some of the phosphorylated residues are also transiently phosphorylated in juvenile brain, but not in more mature stages. Using the monoclonal anti-tau antibodies TAU-1 and AT8, we found in cultured embryonic chicken and rat neurones a clear differential distribution of immunostaining within growing axons. Tau proteins that are phosphorylated at Ser202 (recognized by AT8) appear to be concentrated in the axonal portion that is close to the cell body and they decrease in proximal-distal direction. In contrast, tau proteins carrying an epitope that contains dephospho-Ser202 (recognized by TAU-1) are enriched in the distal axon and the growth cone. In colchicine-treated, growth-inhibited neurones there was an intense TAU-1 staining of the perikarya, but no longer any staining by AT8.

Alzheimer Disease↗
PubMed1995

Developmental expression of tau proteins in the chicken and rat brain: rapid down-regulation of a paired helical filament epitope in the rat cerebral cortex coincides with the transition from immature to adult tau isoforms.

The monoclonal antibodies TAU-1 and AT8 are directed at human microtubule-associated protein tau epitopes that contain a dephosphorylated and phosphorylated Ser202, respectively, while AT180 and AT270 are anti-tau monoclonals with epitopes that require phosphorylated Thr181 and Thr231, respectively. We used these antibodies to study the developmental profiles of tau proteins in rat cerebral cortex and chicken optic lobes. In tau extracts from perinatal rat cerebral cortex. AT8 recognized one major protein band of approximately 50 kDa that peaks on postnatal day 6 and declines rapidly to lower levels at day 12. At later stages, the AT8 epitope was expressed by several adult tau isoforms that were, however, stained only very faintly in highly enriched samples. Two additional tau epitopes recognized by AT180 and AT270 were found to be expressed by one or two protein bands up to about postnatal day 19 and then declined. Unlike the AT8 epitope, in the mature brain these epitopes were stained strongly in enriched samples, where they were expressed by a greater number of adult isoforms. Between embryonic day 19 and postnatal day 12, TAU-1 was found to recognize one major protein band of approximately 50 kDa which migrated slightly faster than the AT8-binding band. At postnatal day 19 and all older stages (including adult cortex), at least three additional TAU-1-binding isoforms with higher apparent molecular weights were present. Hence, the transition from one immature to several adult TAU-1-binding tau isoforms between postnatal day 12 and 19 in rat cerebral cortex coincides with the phase of rapid down-regulation of the AT8 epitope. As in the rat cerebrum, in chicken optic lobes there is a developmental decrease of AT8-binding proteins which is paralleled by striking changes in the electrophoretic pattern of tau isoforms recognized by TAU-1. In both rat cerebral cortex and chicken optic lobes, the period of maximal expression of AT8-binding tau is morphologically characterized by intense axonal growth and beginning synaptogenesis, whereas its subsequent rapid down-regulation and the appearance of novel TAU-1-binding isoforms correlates with synaptic maturation, the onset of spontaneous electrical activity and the beginning of myelination.

Animals↗
PubMed1995

Muscarinic receptor-mediated induction of actin-driven lamellar protrusions in neuroblastoma cell somata and growth cones. Involvement of protein kinase C.

In SH-SY5Y human neuroblastoma cells, addition of acetylcholine or carbachol rapidly induces a transient protrusion of lamellipodia. The protrusions appear after a delay of 30 sec and persist for a period of about 5 min at the margins of cell somata and at the distal parts of cell processes. They are caused by a strikingly increased, cytochalasin B-sensitive assembly of actin at the cell periphery. They often detach from the substrate, retracting and protruding again. In retinoic acid-induced neuronally differentiated cells, this initialized protrusive activity is restricted to growth cones. d-Tubocurarine does not influence, but atropine totally inhibits the cholinergic induction of the actin-driven protrusions, suggesting that a muscarinic receptor-mediated activation of the phosphoinositol signaling pathway is involved. Depolarization by increase of the potassium concentration and ionophore-mediated Ca(2+)-influx are ineffective to trigger the protrusive and ruffling activity. An identical cytochalasin B-sensitive actin-driven response is caused by treating of the cells with the protein kinase C (PKC) activator 12-myristate-13-acetate. In this case, however, lamellar protrusions are formed after a delay of at least 3 min and are maintained for several days. Incubating the cells with the protein kinase C inhibitor bisindolylmaleide or staurosporine inhibits both the muscarinic receptor-mediated and phorbolester-mediated actin-driven response, suggesting that activated PKC plays a crucial role.

Acetylcholine↗
PubMed1994

Expression of a paired helical filament tau epitope in embryonic chicken central nervous system.

Immunoblots from embryonic chicken optic lobes (midbrain) and spinal cord were found to contain different proteins with a molecular weight between 45 and 70 kDa that are recognized by monoclonal antibodies (mAbs) directed at human tau proteins. Each appears as a doublet on SDS-PAGE. The upper, slower migrating bands were recognized by AT8, a monoclonal antibody that requires a phosphorylated Ser-202, an epitope specific for abnormally phosphorylated tau of paired helical filaments (PHF-tau) in Alzheimer brains. The corresponding faster migrating bands were stained by the mAbs BT2 and tau-1, both requiring an epitope containing a non-phosphorylated Ser-202. Phosphatase treatment abolished binding of AT8 and induced an additional binding of tau-1 (and BT2) to the upper bands. Thus, the data suggest that in embryonic chicken central nervous system Ser-202 occurs in a phosphorylated and in a non-phosphorylated state in several distinct tau isoforms.

Animals↗
PubMed1994

Altered ganglioside expression by SH-SY5Y cells upon retinoic acid-induced neuronal differentiation.

SH-SY5Y Neuroblastoma cells were used to study the effect of retinoic acid (RA)-induced differentiation on the expression of gangliosides and neuronal markers. In the presence of 10 microM RA, more than 70% of the cells differentiate to a neuronal phenotype within 8 days. They extend long neuritic processes and show an enhanced immuno-expression of neurone-specific enolase (NSE), neurofilament protein (NF-M), and polysialic acid (PSA). SH-SY5Y cells were found to express at least 12 different gangliosides. RA-induced neuronal differentiation led to a decrease in the content of GM2, GD3, and GD2 and to a 3-7 fold increased concentration of the ganglio-tetraosyl gangliosides GM1, GD1a, GT1a, GD1b, and GT1b. Thus, RA-induced neuronal differentiation of SH-SY5Y cells is accompanied by ganglioside changes similar to those observed during embryonic neuronal differentiation.

Antibodies, Monoclonal↗