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Biomedical subjects

T Winkler

Publications and source records attributed to T Winkler.

At least 37 records · Page 2Linked to original sources
PubMed2000

Precursor B cell receptor-dependent B cell proliferation and differentiation does not require the bone marrow or fetal liver environment.

The capacity of precursor B (pre-B) I cells from fetal liver and bone marrow to proliferate and differentiate into surface immunoglobulin-positive immature B cells in vitro was analyzed. Both fetal liver- and bone marrow-derived progenitors do so in a pre-B cell receptor (pre-BCR)-dependent manner in tissue culture medium alone, without addition of other cells or cytokines. Approximately 20% of the initial pre-B I cells enter more than one division. Analyses at the single-cell level show that approximately 15% divide two to five times. Coculture of pre-B I cells with stromal cells did not enhance proliferation or differentiation, whereas the presence of interleukin 7, especially in combination with stromal cells, resulted mainly in the expansion of pre-B I cells and prevented their further differentiation. Thus, the environment of fetal liver or bone marrow is not required for the pre-BCR to exert its function, which is to select and expand cells that have undergone an inframe V(H)-D(H)J(H) rearrangement that produces a pre-BCR-compatible muH chain. It appears unlikely that a ligand for the pre-BCR drives this pre-B cell proliferation.

Animals↗
PubMed2000

p-Chlorophenylalanine, an inhibitor of serotonin synthesis reduces blood-brain barrier permeability, cerebral blood flow, edema formation and cell injury following trauma to the rat brain.

The role of serotonin in trauma induced alterations in blood-brain barrier (BBB) permeability, cerebral blood flow (CBF), brain edema and cell changes were examined in a new model of cortical injury in the rat using a pharmacological approach. A longitudinal incision into the right parietal cerebral cortex (about 3 mm deep and 5 mm long) was associated with a profound increase in the BBB permeability to Evans blue and [131]I-sodium, brain water content, and a reduction in the CBF in both the ipsilateral and contralateral hemispheres 5 h after trauma. Nissl staining showed a profound nerve cell reaction in the parietal cerebral cortex of both hemispheres. The intensity of these pathological changes was most pronounced in the traumatised hemisphere. Pretreatment with p-CPA, a serotonin synthesis inhibitor, significantly attenuated breakdown of the BBB permeability, brain edema and the CBF disturbances. Damaged and distorted nerve cells were markedly less frequent in p-CPA treated rats. This effect of the drug was most pronounced in the contralateral hemisphere. The observations strongly suggest that serotonin is one of the important neurochemical mediators of BBB permeability disturbances and brain edema formation in the trauma induced brain damage.

Animals↗
PubMed2000

Neurotrophic factors attenuate alterations in spinal cord evoked potentials and edema formation following trauma to the rat spinal cord.

Influence of brain derived neurotrophic factor (BDNF) and insulin like growth factor-1 (IGF-1) on spinal cord injury induced disturbances in spinal cord conduction, edema formation and cellular stress response was examined in a rat model. Pretreatment with BDNF or IGF-1 significantly attenuated the loss of SCEP negative amplitude seen immediately after spinal cord injury. In these neurotrophins treated rats, upregulation of heat shock protein (HSP 72 kD) immunoreactivity, a measure of cellular stress response and spinal cord edema formation were considerably reduced 5 h after injury. These results suggest that neurotrophic factors improve spinal cord conduction after trauma and this beneficial effect of growth factors may be related with their ability to attenuate trauma induced cellular stress response, not reported earlier.

Animals↗
PubMed2000

Growth hormone attenuates alterations in spinal cord evoked potentials and cell injury following trauma to the rat spinal cord. An experimental study using topical application of rat growth hormone.

The influence of exogenous rat growth hormone on spinal cord injury induced alterations in spinal cord evoked potentials (SCEP) and edema formation was examined in a rat model. Repeated topical application of rat growth hormone (20microl of 1microg/ml solution) applied 30min before injury and at 0min (at the time of injury), 10min, 30min, 60min, 120min, 180min, and 240min, resulted in a marked preservation of SCEP amplitude after injury. In addition, the treated traumatised cord showed significantly less edema and cell changes. These observations suggest that growth hormone has the capacity to improve spinal cord conduction and attenuate edema formation and cell injury in the cord indicating a potential therapeutic implication of this peptide in spinal cord injuries.

Animals↗
PubMed2000

Theta oscillations and the ERP old/new effect: independent phenomena?

OBJECTIVES: The hypothesis is examined whether a memory-related change in induced band power (oscillatory old/new effect) is functionally related to a memory-related increase in ERP positivity (ERP old/new effect). METHODS: In order to avoid a confounding on the measurement level, induced band power (IBP) was used as a measure that is devoid of the influence of evoked components. The EEG was recorded during a recognition memory task. RESULTS: The results show that compared to correctly rejected words, targets (remembered words) elicit a significantly larger P300. An oscillatory old/new effect was found for the delta and theta but not for the alpha band. It is manifested by an increase in delta and theta IBP which is significantly larger for targets than for correctly rejected words. It can be observed during the same time interval and shows the same topographic distribution as the ERP old/new effect. Most importantly, however, the ERP old/new effect (as well as the P300 itself) is generated by very slow frequencies which lie below the delta band. CONCLUSIONS: These findings demonstrate that the two types of old/new effects are functionally related. Possible physiological mechanisms underlying this relationship are discussed in terms of a threshold change in the cortex (generating the P300) that occurs during an increase in hippocampal theta activity (generating an increase in induced theta power).

Adult↗
PubMed2000

Role of apoptosis in autoimmunity.

Apoptosis is a physiological form of cell death required to ensure that the rate of cell division is balanced by the rate of cell death in multicellular organisms. Dysregulation of apoptosis is associated with the pathogenesis of a wide array of diseases: cancer, neurodegeneration, autoimmunity, heart disease and others. In this review we collect arguments supporting a hypothesis of a dysregulated apoptosis leading to development of autoimmunity like systemic lupus erythematosus (SLE). This notion is supported by occurence of known autoantigens in apoptotic blebs, in vitro findings of an increased rate of apoptotic lymphoblasts despite optimal cytokine stimulation combined with a defective in vitro clearance of apoptotic bodies by SLE phagocytes. Moreover, we and others could generate histone-specific lymphocytic cell lines from cells after activation with autologous apoptotic material. These lymphocytes could stimulate autologous B-lymphocytes to produce of anti-dsDNA antibodies, a diagnostic hallmark for SLE. Finally, antibodies against phospholipids like phosphatidylserine are often associated with systemic autoimmunopathies like SLE and others. Phosphatidylserine is exposed on apoptotic cells as early sign of programmed cell death and serves as phagocyte recognition molecule for apoptotic cells. Formation of immune complexes and deposition in tissues might lead to organ damage and disease. This scenario will be discussed in this review in detail.

Animals↗
PubMed2000

Etiopathogenesis of systemic lupus erythematosus.

Systemic lupus erythematosus is an autoimmune disease of unknown etiology. Research efforts of the last few years have mainly focused on basic molecular and cellular pathogenetic processes of the disease. Consequently, this paper reviews the etiopathogenetic hallmarks, such as impaired amount and presentation of nuclear antigens, production of antinuclear antibodies by T-cell-dependent B cell stimulation and organ damage by anti-dsDNA antibodies or immune complexes that are discussed at the present time. In summary, the hypothesis of a dysregulation of apoptotic cell clearance is strongly supported and broadly discussed.

Animals↗
PubMed1999

Hematopoietic growth factors signal through the formation of reactive oxygen species.

Hematopoietic growth factors (HGFs) stimulate growth, differentiation, and prevent apoptosis of progenitor cells. Each growth factor has a specific cell surface receptor, which activates both unique and shared signal transduction pathways. We found that several HGFs, including granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3), steel factor (SF), and thrombopoietin (TPO) induce a rapid increase in reactive oxygen species (ROS) in quiescent cells. In an effort to understand the potential biochemical and biological consequences of increased ROS in these cells, we exposed growth factor-deprived cells to hydrogen peroxide (H2O2) at concentrations that increased intracellular ROS. H2O2 induced a dose-dependent increase in tyrosine phosphorylation, including increased tyrosine phosphorylation of the GM-CSF receptor beta chain (betac), STAT5, and other signaling proteins. H2O2 also induced expression of the early response gene c-FOS, and G1- to S-phase transition, but not S- to G2/M-phase transition of MO7e cells. The cell permeable antioxidant pyrrolidine dithiocarbamate (PDTC) decreased the intracellular levels of ROS and inhibited tyrosine phosphorylation induced by GM-CSF in MO7e cells, suggesting that ROS generation plays an important role in GM-CSF signaling. Consistent with this notion, PDTC and two other antioxidants, N-acetyl cysteine and 2-mercaptoethanol, reduced growth and viability of MO7e cells. These results suggest that generation of ROS in response to HGFs may contribute to downstream signaling events, especially those involving tyrosine phosphorylation.

Acetylcysteine↗
PubMed1999

Confocal fluorescence coincidence analysis: an approach to ultra high-throughput screening.

Fluorescence-based assay technologies play an increasing role in high-throughput screening. They can be classified into different categories: fluorescence polarization, time-resolved fluorescence, fluorescence resonance energy transfer, and fluorescence correlation spectroscopy. In this work we present an alternative analytical technique for high-throughput screening, which we call confocal fluorescence coincidence analysis. Confocal fluorescence coincidence analysis extracts fluorescence fluctuations that occur coincidently in two different spectral ranges from a tiny observation volume of below 1 fl. This procedure makes it possible to monitor whether an association between molecular fragments that are labeled with different fluorophores is established or broken. Therefore, it provides access to the characterization of a variety of cleavage and ligation reactions in biochemistry. Confocal fluorescence coincidence analysis is a very sensitive and ultrafast technique with readout times of 100 ms and below. This feature is demonstrated by means of a homogeneous assay for restriction endonuclease EcoRI. The presented achievements break ground for throughput rates as high as 10(6) samples per day with using only small amounts of sample substance and therefore constitute a solid base for screening applications in drug discovery and evolutionary biotechnology.

Base Sequence↗
PubMed1999

On the suitability of fiberglass reinforced polyester as building material for mesocosms.

Gel- and topcoat surface layers on fiberglass [glass-reinforced plastic (GRP)] made of unsaturated resin based on isophthalic acid polyester and neopentyl glycol (ISO-NPG) were tested for leaching, ecotoxicity of water eluates, and abrasion by river sediments at a current speed of 0.5 m * s-1. Leaching from topcoat tempered at low temperature was significant, whereas it was negligible from highly tempered gelcoat. Water eluates from both gel-and topcoat were nontoxic in routinely employed biotests (bacteria, algae, daphnids). No abrasion by river sediments was detectable. Based on these results, GRP with gelcoat made of ISO-NPG is considered a suitable building material for mesocosms.

Acetone↗
PubMed1999

'Paradoxical' alpha synchronization in a memory task.

The results of a specially designed memory search paradigm which maximizes episodic short-term memory (STM) and minimizes semantic long-term memory (LTM) demands show that the upper alpha band synchronizes selectively in those conditions and time intervals where episodic STM demands are maximal. This finding of a selective alpha synchronization occurring only in the upper alpha band and during highest task demands is surprising because it is well known that usually alpha desynchronizes during mental activity. Because experiments from our laboratory indicate that desynchronization in the upper alpha band is related to semantic LTM processes, the present finding suggests that a selective synchronization in this frequency band reflects inhibition of semantic LTM. It is assumed that once the capacity limits of STM are reached or exceeded, processing resources are no longer distributed and that potentially interfering, task irrelevant, brain areas or processing systems are inhibited.

Adult↗
PubMed1999

Psychomotor retardation and anhedonia in depression.

Anhedonia, the inability to experience pleasure, and observed changes in psychomotor performance are frequent psychopathological phenomena in major depression with possible common neurobiological mechanisms. Interest, pleasure and reactivity to pleasurable stimuli contribute to movement generation and observable behaviour. Therefore the relationship between anhedonia and psychomotor retardation was studied in 48 depressed patients. Subjectively experienced anhedonia correlated with self-rated but not with observer-rated global severity of depression. There was a significant correlation between anhedonia and psychomotor retardation assessed with the Widöcher Retardation Scale. The results suggest the existence of an empirical relationship between reduced ability to experience pleasure and observable psychomotor retardation in depression. Specific measures of psychomotor phenomena may provide further insights into the relationship between observable behaviour and self-experienced symptoms in depression.

Adult↗
PubMed1999

Pathogenesis of borna disease virus: granulocyte fractions of psychiatric patients harbor infectious virus in the absence of antiviral antibodies.

Borna disease virus (BDV) causes acute and persistent infections in various vertebrates. During recent years, BDV-specific serum antibodies, BDV antigen, and BDV-specific nucleic acid were found in humans suffering from psychiatric disorders. Furthermore, viral antigen was detected in human autopsy brain tissue by immunohistochemical staining. Whether BDV infection can be associated with psychiatric disorders is still a matter of debate; no direct evidence has ever been presented. In the present study we report on (i) the detection of BDV-specific nucleic acid in human granulocyte cell fraction from three different psychiatric patients and (ii) the isolation of infectious BDV from these cells obtained from a patient with multiple psychiatric disorders. In leukocyte preparations other than granulocytes, either no BDV RNA was detected or positive PCR results were obtained only if there was at least 20% contamination with granulocytes. Parts of the antigenome of the isolated virus were sequenced, demonstrating the close relationship to the prototype BDV strains (He/80 and strain V) as well as to other human virus sequences. Our data provide strong evidence that cells in the granulocyte fraction represent the major if not the sole cell type harboring BDV-specific nucleic acid in human blood and contain infectious virus. In contrast to most other reports of putative human isolates, where sequences are virtually identical to those of the established laboratory strains, this isolate shows divergence in the region previously defined as variable in BDV from naturally infected animals.

Antibodies, Viral↗
PubMed1999

BCR/ABL directly inhibits expression of SHIP, an SH2-containing polyinositol-5-phosphatase involved in the regulation of hematopoiesis.

The BCR/ABL oncogene causes chronic myelogenous leukemia (CML), a myeloproliferative disorder characterized by clonal expansion of hematopoietic progenitor cells and granulocyte lineage cells. The SH2-containing inositol-5-phosphatase SHIP is a 145-kDa protein which has been shown to regulate hematopoiesis in mice. Targeted disruption of the murine SHIP gene results in a myeloproliferative syndrome characterized by a dramatic increase in numbers of granulocyte-macrophage progenitor cells in the marrow and spleen. Also, hematopoietic progenitor cells from SHIP(-/-) mice are hyperresponsive to certain hematopoietic growth factors, a phenotype very similar to the effects of BCR/ABL in murine cells. In a series of BCR/ABL-transformed hematopoietic cell lines, Philadelphia chromosome (Ph)-positive cell lines, and primary cells from patients with CML, the expression of SHIP was found to be absent or substantially reduced compared to untransformed cell lines or leukemia cells lacking BCR/ABL. Ba/F3 cells in which expression of BCR/ABL was under the control of a tetracycline-inducible promoter showed rapid loss of p145 SHIP, coincident with induction of BCR/ABL expression. Also, an ABL-specific tyrosine kinase inhibitor, CGP57148B (STI571), rapidly caused reexpression of SHIP, indicating that BCR/ABL directly, but reversibly, regulates the expression of SHIP protein. The estimated half-life of SHIP protein was reduced from 18 h to less than 3 h. However, SHIP mRNA also decreased in response to BCR/ABL, suggesting that SHIP protein levels could be affected by more than one mechanism. Reexpression of SHIP in BCR/ABL-transformed Ba/F3 cells altered the biological behavior of cells in culture. The reduction of SHIP due to BCR/ABL is likely to directly contribute to the pathogenesis of CML.

Animals↗
PubMed1998

Affinities of mAbs to Tet repressor complexed with operator or tetracycline suggest conformational changes associated with induction.

We isolated five monoclonal antibodies (mAbs) made against tetracycline repressor (TetR), one against the TetR tetracycline complex (Tc) and two against the TetR-tet operator (tetO) complex. The epitopes of the anti-TetR mAbs are localized in the alpha-helix-turn-alpha-helix motif (HTH), at different sites near the Tc binding pocket and at the dimerization interface. The anti-TetR-Tc and one of the anti-TetR-tetO mAbs recognize epitopes near the Tc binding pocket. The other anti-TetR-tetO mAb binds to an epitope within the HTH. Quantitative immunoprecipitation and competitive ELISA employing TetR, TetR-Tc, or TetR-tetO revealed different affinities of the mAbs for TetR in these functional states. Binding of the two mAbs to epitopes in the HTH was identical for TetR and TetR-Tc indicating the same conformation in both forms. The epitope located in the dimerization interface is bound more strongly in TetR compared to TetR-Tc, supporting the idea of different conformations of that epitope in these forms of TetR. The greatest affinity differences were found for epitopes around the Tc binding pocket. Two anti-TetR mAbs have the highest affinities for free TetR, somewhat reduced affinity for TetR-tetO and the lowest affinities for TetR-Tc. The anti-TetR-Tc mAb has a discontinuous epitope, formed in TetR-Tc, which is less well bound in TetR and not bound in the TetR-tetO complex. One anti-TetR-tetO mAb does not recognize TetR-Tc. Since the epitopes do not overlap with the respective ligand binding sites on TetR, these results are interpreted as conformational differences of the epitopes in these forms of TetR.

Animals↗
PubMed1998

Theta synchronization in the human EEG and episodic retrieval.

Event-related desynchronization (ERD) and synchronization (ERS) was measured during episodic retrieval in a specially designed recognition task which forces subjects to avoid semantic search strategies. ERD represents the percentage of a decrease, ERS an increase in band power. The results show that only the theta band differentiates between good and bad episodic memory performers and that good performance is related to a large degree of theta synchronization. The delta and alpha bands did not yield significant effects. Topographical differences in theta ERS reveal that good performers use primarily their right hemisphere to retrieve episodic information. This finding agrees with respective results from PET studies.

Adult↗
PubMed1998

Dermatan sulfate released after injury is a potent promoter of fibroblast growth factor-2 function.

Proteoglycans have been shown in vitro to bind multiple components of the cellular microenvironment that function during wound healing. To study the composition and function of these molecules when derived from an in vivo source, soluble proteoglycans released into human wound fluid were characterized and evaluated for influence on fibroblast growth factor-2 activity. Immunoblot analysis of wound fluid revealed the presence of syndecan-1, syndecan-4, glypican, decorin, perlecan, and versican. Sulfated glycosaminoglycan concentrations ranged from 15 to 65 microgram/ml, and treatment with chondroitinase B showed that a large proportion of the glycosaminoglycan was dermatan sulfate. The total glycosaminoglycan mixture present in wound fluid supported the ability of fibroblast growth factor-2 to signal cell proliferation. Dermatan sulfate, and not heparan sulfate, was the major contributor to this activity, and dermatan sulfate bound FGF-2 with Kd = 2.48 microM. These data demonstrate that proteoglycans released during wound repair are functionally active and provide the first evidence that dermatan sulfate is a potent mediator of fibroblast growth factor-2 responsiveness.

Body Fluids↗