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Biomedical subjects

M Weiler

Publications and source records attributed to M Weiler.

At least 19 recordsLinked to original sources
PubMed2005

BCL-xL: time-dependent dissociation between modulation of apoptosis and invasiveness in human malignant glioma cells.

Conditionally BCL-xL-overexpressing LNT-229 Tet-On glioma cell clones were generated to investigate whether the 'antiapoptosis phenotype' and the 'motility phenotype' mediated by BCL-2 family proteins in glioma cells could be separated. BCL-xL induction led to an immediate and concentration-dependent protection of LNT-229 cells from apoptosis. BCL-xL induction for up to 3 days did not result in altered invasiveness. In contrast, long-term BCL-xL induction for 21 days resulted in increased transforming growth factor-beta2 expression, and in metalloproteinase-2 and -14 dependent, but integrin independent, increased invasiveness. Withdrawal of doxycycline (Dox) abolished the protection from apoptosis whereas the 'invasion phenotype' remained stable. Dox stimulation of BCL-xL-inducible LNT-229 cells conferred infiltrative growth to BCL-xL-positive glioma cells in vivo and reduced the survival of tumor-bearing mice. These data allow to dissect a direct antiapoptotic action of BCL-xL from an indirect effect, presumably mediated by altered gene expression, which modifies tumor cell invasiveness in vitro and in vivo.

Animals↗
PubMed2001

Strong association of a novel Tau promoter haplotype in progressive supranuclear palsy.

The microtubule associated protein, tau, is found in fibrillar lesions that characterise progressive supranuclear palsy (PSP) and related tauopathies. Mutations in the tau gene in frontotemporal dementia with parkinsonism linked to chromosome 17 (FTDP-17) and genetic association of the H1 haplotype of the tau gene with PSP has firmly established a direct role for tau in disease pathogenesis. However, the functional significance of the tau genetic association in PSP is unknown. We analysed the tau gene promoter sequence and identified two novel single nucleotide polymorphisms. Here we report the genetic association of a novel tau promoter haplotype with PSP which may influence tau transcription.

DNA Mutational Analysis↗
PubMed2001

Interleukin-15 is the main mediator of lymphocyte proliferation in cultures mixed with human kidney tubular epithelial cells.

BACKGROUND: Interleukin- (IL) 15 is a potent non-T cell-derived cytokine with IL-2-like activities. Elevated levels of IL-15 expression were observed in biopsies of acutely rejected human kidney grafts. We tested the role of IL-15 in mixed lymphocyte kidney reaction (MLKR) and the effects of immunosuppressive drugs on this reaction. METHODS: Primary cultures of human tubular epithelial cells (TEC) were stimulated by interferon-gamma and treated with cyclosporin A (CsA, 10-1000 ng/ml), rapamycin (Rapa, 2.5-10 ng/ml), and dexamethasone (Dex, 10-10-10-7 M). IL-15 levels were measured by ELISA. To induce MLKR, we seeded OKT3-prestimulated allogenic human peripheral blood mononuclear cells (PBMC) on a monolayer of TEC in the presence of CsA (25-250 ng/ml), Rapa (0.25-1 ng/ml), and Dex (10-10-10-7 M). PBMC proliferation was quantified by 3H-thymidine incorporation. RESULTS: CsA, Dex, and Rapa had no effect on IL-15 production by TEC. The presence of TEC induced marked proliferation of PBMC. Pretreatment of TEC with IFN-gamma enhanced MLKR in direct correlation with the increased IL-15 levels. MLKR was blocked by anti-IL-15, but not significantly by anti-IL-2 monoclonal antibody. Contrary to Rapa and Dex, CsA failed to inhibit MLKR CONCLUSIONS: IL-15 is a major mediator of lymphocyte proliferation in MLKR. Its production by TEC was unaffected by CsA, Rapa, and Dex. However, IL-15 activity is effectively inhibited by Rapa and Dex but not by CsA. The diversity in the effects of the various drugs is probably related to the different mechanisms. Our results support the possible involvement of renal IL-15 in graft rejection and suggest that resistance to CsA treatment is related to its failure to decrease IL-15 activity.

Cells, Cultured↗
PubMed2001

Sequential regional cerebral blood flow brain scans using PET with H2(15)O demonstrate ketamine actions in CNS dynamically.

The aim of this study was to examine the potential of serial rCBF studies to directly characterize the regional effects and dynamic time course of the centrally active drug ketamine. The value of a broader application of this technique to other neurally active drugs to characterize the pharmacodynamics of CNS compounds is suggested by these data. Thirteen normal subjects received a 0.3 mg/kg intravenous dose of ketamine over 60 seconds; ten other individuals received placebo in the same manner. For each subject, three baseline PET rCBF scans and seven sequential post-ketamine scans at 10-minute intervals were obtained using H(2)(15)O water. SPM techniques were employed to identify the maxima of any cluster significant by spatial extent analysis at any post-ketamine time point between 0 and 36 min. These extremes from the ketamine group, were identified in placebo scans similarly and grown to a 6x6x12 mm voxel set. The average rCBF values of the ketamine-defined clusters were determined in the drug and placebo conditions at all time points. rCBF across time was plotted for each cluster and compared between drug and placebo. Area under the curve (AUC) was calculated between baseline and 36 minutes. The kinetic characteristics of the ketamine-induced rCBF curves were compared to induced behaviors in each maxima. Ketamine produced distinct patterns of rCBF change over time in different brain regions; maxima within an anatomically defined region responded similarly. Ketamine induced rCBF activations in anterior cingulate, medial frontal and inferior frontal cortices. All maxima with a relative flow reduction with ketamine were in the cerebellum. The pattern of all activations and suppressions was monophasic with the peak changes at 6-16 minutes. In preliminary analysis, individual C(max) and AUC of maxima in the anterior cingulate/medial frontal region tended to correlate with the mild psychotomimetic action of ketamine; whereas, there was no tendency toward correlation with this psychological change in cerebellar maxima. The direct action of a centrally active drug can be assessed regionally and dynamically in brain using rCBF and a scan sequence optimally timed to complement the drug's time course. Ketamine pharmacodynamic response can be related to concurrent behavioral changes, tending to link the behavior with a brain region. This experimental design provides direct characterization of drug action in the CNS in ways heretofore unavailable.

Adult↗
PubMed2000

Adhesion induced expression of the serine/threonine kinase Fnk in human macrophages.

Members of the polo subfamily of protein kinases play crucial roles in cell proliferation. To study the function of this family in more detail, we isolated the cDNA of human Fnk (FGF-inducible kinase) which codes for a serine/threonine kinase of 646 aa. Despite the homology to the proliferation-associated polo-like kinase (Plk), tissue distribution of Fnk transcripts and expression kinetics differed clearly. In contrast to Plk no correlation between cell proliferation and Fnk gene expression was found. Instead high levels of Fnk mRNA were detectable in blood cells undergoing adhesion. The transition of monocytes from peripheral blood to matrix bound macrophages was accompanied by increasing levels of Fnk with time in culture. Neither treatment of monocytes with inducers of differentiation nor withdrawal of serum did influence Fnk mRNA levels significantly, suggesting that cell attachment triggers the onset of Fnk gene transcription. The idea that Fnk is part of the signalling network controlling cellular adhesion was supported by the analysis of the cytoplasmic distribution of the Fnk protein and the influence of its overexpression on the cellular architecture. Fnk as fusion protein with GFP localized at the cellular membrane in COS cells. Dysregulated Fnk gene expression disrupted the cellular f-actin network and induced a spherical morphology. Furthermore, Fnk binds to the Ca2+/integrin-binding protein Cib in two-hybrid-analyses and co-immunoprecipitation in assays. Moreover, both proteins were shown to co-localize in mammalian cells. The homology of Cib with calmodulin and with calcineurin B suggests that Cib might be a regulatory subunit of polo-like kinases.

Actins↗
PubMed2000

Accessory role of human peritoneal mesothelial cells in antigen presentation and T-cell growth.

BACKGROUND: To assess the role of human peritoneal mesothelial cells (HPMCs) in the generation of an immune response during peritonitis, we tested their ability to activate T-cells by antigen presentation (AP) and by the secretion of interleukin-15 (IL-15). IL-15 is a potent leukocyte activator that stimulates the proliferation of CD4+, CD8+, and B and natural killer (NK) cells. METHODS: HPMCs and mononuclear cells were derived from six volunteer patients who underwent elective abdominal surgery. Flow cytometry was used to analyze human lymphocyte antigen-DR (HLA-DR), intercellular adhesion molecule-1 (ICAM-1), and B7 molecules on HPMCs. Affinity-purified CD4 cells were used for AP assays. We used a specific enzyme-linked immunosorbent assay to detect interferon-gamma (IFN-gamma), IL-2, and IL-15 protein and reverse transcription-polymerase chain reaction for mRNA analysis. RESULTS: HPMCs expressed HLA-DR molecules following IFN-gamma treatment. ICAM-1 molecules were expressed at high levels, and B7-1 and B7-2 molecules could not be detected. The accessory function of HPMCs was assayed by T-cell stimulation using anti-CD3 antibodies (OKT3). HPMCs were essential for a significant OKT3-induced T-cell proliferation. Anti-ICAM-1 antibodies blocked OKT3-induced proliferation. HPMCs served as effective antigen-presenting cells when Tetanus toxoid (TT) or Staphylococcus aureus-alpha-toxin were used as antigens. IFN-gamma, IL-2, and IL-15 accumulated during AP reactions. We found that IL-15 is produced by HPMCs, and IFN-gamma up-regulated its mRNA levels and protein secretion in a dose-dependent manner. We also detected IL-15 in the peritoneal effluent of patients undergoing continuous peritoneal dialysis treatment. In patients suffering from peritonitis, IL-15 levels were elevated (35.0 +/- 6.0 pg/mL, N = 10) as compared with noninfected patients (16.2 +/- 4.0 pg/mL, N = 7). CONCLUSIONS: HPMCs participate in the peritoneal immune response against invading pathogens by AP. For this process, ICAM-1 is the major accessory molecule. In addition, HPMCs may contribute to T-cell activation by secretion of IL-15.

Adult↗
PubMed2000

Brain activation patterns in schizophrenic and comparison volunteers during a matched-performance auditory recognition task.

OBJECTIVE: The biological characteristics of schizophrenia are often studied by using functional imaging techniques. However, since volunteers with schizophrenia routinely fail to perform as accurately or as quickly as healthy volunteers, it is difficult to ascertain whether a particular deficit in blood flow to a brain region is due to behavior or to the underlying illness. In this report, investigators used an auditory recognition task to assess brain blood flow patterns and behavioral correlates of schizophrenic patient volunteers trained on the task. METHOD: Twelve healthy volunteers and 18 volunteers with schizophrenia were trained to make tone frequency recognitions. Accuracy and stimuli were matched between groups. Participants were required to press a button to indicate whether a briefly presented tone was the high-frequency (1500 Hz) reference tone or one of a lower frequency level (level chosen to elicit an 80% accuracy score). Subjects underwent bolus [(15)O]H(2)O blood flow positron emission tomography during inactive rest, a sensory motor control condition, and the decision task. Blood flow patterns were assessed between conditions and between groups. RESULTS: As a group, the patients with schizophrenia (who performed as quickly and accurately as the comparison subjects) exhibited significantly less change in regional cerebral blood flow (rCBF) to the anterior cingulate and supplementary motor cortices when switching from the sensory motor control to the decision condition. There were also marked between-group differences in correlations between rCBF and response time. Whereas the comparison subjects exhibited progressively greater blood flow to the frontal cortex in association with longer response times, the schizophrenic patients exhibited progressively lower blood flow in conjunction with extended response times. CONCLUSIONS: The failure to appropriately enhance cingulate activity when engaged in a demanding task and the progressive, time-dependent decline in frontal blood flow suggest that patients with schizophrenia are unable to make optimal use of frontocingulate systems when maximally engaged in high-error tasks.

Adult↗
PubMed1999

The polo-like protein kinases Fnk and Snk associate with a Ca(2+)- and integrin-binding protein and are regulated dynamically with synaptic plasticity.

In order to stabilize changes in synaptic strength, neurons activate a program of gene expression that results in alterations of their molecular composition and structure. Here we demonstrate that Fnk and Snk, two members of the polo family of cell cycle associated kinases, are co-opted by the brain to serve in this program. Stimuli that produce synaptic plasticity, including those that evoke long-term potentiation (LTP), dramatically increase levels of both kinase mRNAs. Induced Fnk and Snk proteins are targeted to the dendrites of activated neurons, suggesting that they mediate phosphorylation of proteins in this compartment. Moreover, a conserved C-terminal domain in these kinases is shown to interact specifically with Cib, a Ca(2+)- and integrin-binding protein. Together, these studies suggest a novel signal transduction mechanism in the stabilization of long-term synaptic plasticity.

Amino Acid Sequence↗
PubMed1999

Stimulation of lysosomal sphingomyelin degradation by sphingolipid activator proteins.

Lysosomal breakdown of glycosphingolipids with short hydrophilic carbohydrate headgroups is achieved by the simultaneous action of specific hydrolases and sphingolipid activator proteins (SAPs). Activator proteins are considered to facilitate the enzyme/substrate interaction between water-soluble enzymes and membrane-bound substrates. Sphingomyelin, containing the small hydrophilic phosphorylcholine moiety, is hydrolysed by acid sphingomyelinase (acid SMase). Recent experimental data on the in vivo and in vitro role of activator proteins in sphingomyelin breakdown by acid SMase are reviewed. These data combined with the results using homogenous protein preparations as well as a liposomal assay system mimicking the physiological conditions suggest that lysosomal sphingomyelin degradation is not critically dependent on any of the known activator proteins. Moreover, evidence is provided that the assumed intramolecular activator domain of acid SMase and especially the presence of negatively charged lipids in the lysosomes are sufficient for sphingomyelin turnover.

Animals↗
PubMed1999

Effects of cognitive treatment in psychiatric rehabilitation.

Ninety subjects with severe and disabling psychiatric conditions, predominantly schizophrenia, participated in a controlled-outcome trial of the cognitive component of Integrated Psychological Therapy (IPT), a group-therapy modality intended to reestablish basic neurocognitive functions. The cognitive therapy was delivered to subjects in the experimental condition during intensive 6-month treatment periods. Control subjects received supportive group therapy. Before, during, and after the intensive treatment period, all subjects received an enriched regimen of comprehensive psychiatric rehabilitation, including social and living skills training, optimal pharmacotherapy, occupational therapy, and milieu-based behavioral treatment. IPT subjects showed incrementally greater gains compared with controls on the primary outcome measure, the Assessment of Interpersonal Problem-Solving Skills, suggesting that procedures that target cognitive impairments of schizophrenia spectrum disorders can enhance patients' response to standard psychiatric rehabilitation, at least in the short term, in the domain of social competence. There was equivocal evidence for greater improvement in the experimental condition on the Brief Psychiatric Rating Scale disorganization factor and strong evidence for greater improvement on a laboratory measure of attentional processing. There was significant improvement in both conditions on measures of attention, memory, and executive functioning, providing support for the hypothesis that therapeutic procedures that target impaired cognition enhance response to conventional psychiatric rehabilitation modalities over a 6-month timeframe.

Adolescent↗
PubMed1999

Transcription factors Sp1 and AP-2 mediate induction of acid sphingomyelinase during monocytic differentiation.

Cells from the human monocytic leukemia cell line THP-1 differentiate towards a macrophage-like phenotype when stimulated with phorbol 12-myristate -13- acetate (PMA), 1,25-dihydroxy-vitamin D3, and various other agents. We demonstrate here that the expression of the lysosomal enzyme acid sphingomyelinase (ASM; E.C. 3.1.4.12) is induced during this process and is strongly elevated in differentiated THP-1 cells, as well as in differentiated human mononuclear phagocytes. Using Northern blotting, RNase protection assay, and nuclear run-on analyses, we show that the up-regulation of ASM expression is regulated mainly at the level of transcription and that new protein synthesis is required for enhanced ASM activity. This cell-type specific induction by PMA treatment was further investigated with respect to transcriptional control. A series of 5' deletion derivatives of the upstream regulatory region were used in transient transfection assays to identify promoter elements required for basal and inducible gene expression. A PMA responsive element was localized to a region between -319 and -219 bp upstream of the initiation codon and co-transfections with transcription factor expression plasmids for AP-2 and Sp1 resulted in augmented ASM promoter activity, which was abolished when the binding sites for these two factors were deleted. Using electrophoretic mobility shift assays and supershift assays we demonstrate that this region is specifically bound by Sp1 and AP-2. These factors are present in nuclear extracts prepared from both induced and uninduced THP-1 cells. However, the intensity of the complex formed appeared to increase when nuclear extracts from PMA-treated cells were used. From these studies, we conclude that a concerted action of the transcription factors AP-2 and Sp1 is essential for the up -regulation of ASM expression during the process of macrophage differentiation.

Base Sequence↗
PubMed1998

Effects of the D3 and autoreceptor-preferring dopamine antagonist (+)-UH232 in schizophrenia.

The aminotetralin derivative (+)-UH232 is a dopamine-receptor antagonist with complex pharmacological properties, including a 4:1 selectivity for the D3 vs. D2 receptor and a preference for the autoreceptors. Its behavioral profile differs markedly from that of other dopamine antagonists in exhibiting both stimulant and inhibitory features. In an effort to elucidate the role of different dopamine receptor subtypes in psychosis, we administered (+)-UH232 to drug-free schizophrenic patients. Six patients received single doses of (+)-UH232 over a dose range of 80 to 180 mg in a rising-dose, double-blind placebo-controlled design. Efficacy and safety were assessed over 8 hours after a single dose. In none of the patients at any of the doses was there an indication of a symptomatic psychosis improvement in response to (+)-UH232. On the contrary, an examination of individual cases revealed symptomatic worsening, such as increases in unusual thought content, anxiety, activation and hostility in four patients. No extrapyramidal movements were noted. Safety assessments were benign. These preliminary data suggest that putative dopamine D3 antagonism, in combination with preferential autoreceptor antagonism, does not alleviate but rather tends to worsen psychosis, at least following a single-dose regimen. However, the possibility cannot be excluded that a 5-HT2- receptor agonistic action of (+)-UH232, suggested by some animal data, has played a role in this treatment outcome. Replication with more selective agents and multiple dose regimens is necessary.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1998

Interleukin-15, a leukocyte activator and growth factor, is produced by cortical tubular epithelial cells.

Many renal diseases, including transplant rejection, are mediated by mononuclear cells. Interleukin-15 (IL-15) has been recently described as a cytokine with IL-2-like activity. IL-15 is an effective leukocyte growth factor, activator, and chemoattractant. In rejected human kidney allografts, elevated IL-15, but not IL-2, mRNA is expressed, suggesting a role for IL-15 in the rejection process. The aim of this study was to investigate whether human cortical tubular epithelial cells (HTC) are able to produce IL-15 and whether IL-15 expression is regulated by inflammatory mediators. HTC were isolated and characterized, and IL-15 expression was analyzed by reverse transcription-PCR, enzyme-linked immunosorbent assay, and bioactivity. It was found that HTC constitutively express IL-15. Upon stimulation of HTC with interferon-gamma (IFN gamma), the levels of both mRNA and protein increased up to twofold. In contrast, lipopolysaccharide, IL-1, IL-2, and tumor necrosis factor-alpha had no detectable effect. IFN gamma action on HTC was dose-dependent from concentrations of 5 U/ml, reaching a plateau at 50 U/ml. HTC supernatants induced proliferation of the T cell line CTLD, which could be partially blocked (50%) by specific IL-15 antibodies. This study shows that IL-15 is secreted by HTC and that the Th1-cytokine IFN gamma upregulates IL-15 expression. This suggests that HTC play a role in cell-mediated renal diseases by releasing IL-15.

Base Sequence↗
PubMed1995

Molecular analysis of the acid sphingomyelinase deficiency in a family with an intermediate form of Niemann-Pick disease.

A novel point mutation in the lysosomal acid sphingomyelinase gene has been identified in the recently reported Serbian family with a clinically and biochemically atypical intermediate form of Niemann-Pick disease. The mutation was a T1171-->G transversion resulting in substitution of glycine for normal tryptophan at amino acid residue 391. The coding sequence was otherwise normal. All of the five affected individuals were almost certainly homoallelic, and both of the two obligate heterozygotes studied also carried the same mutation. This mutation is therefore likely to be directly associated with the atypical phenotype of these patients. Expression in COS-1 cells suggested a higher residual activity than that in cultured fibroblasts. A recently developed high-affinity rabbit antihuman sphingomyelinase antibody allowed us to study for the first time the biosynthesis, processing, and targeting of a mutant sphingomyelinase by metabolic labeling of cultured fibroblasts. The mutant enzyme protein was normally synthesized, processed, and routed to the lysosome but was apparently unstable and degraded rapidly once it reached the lysosome. Together with the finding of the relatively high residual activity in COS-1 cells, we interpret our observations to mean that instability and rapid breakdown of the mature mutant enzyme protein, due to the mutation rather than direct inactivation of the catalytic activity, is the primary mechanism for the deficiency of sphingomyelinase activity in these patients. A high prevalence of this mutation in the Serbian population is likely, since the family pedigree indicates that members from four reportedly unrelated families must have contributed the same mutation.

Base Sequence↗
PubMed1994

Changing cognitive functioning in rehabilitation of schizophrenia.

A three-factor model is proposed for clinical assessment of cognitive and neuropsychological impairments in schizophrenia. The first factor is stable, pervasive and vulnerability-linked. The second and third include executive, memory and conceptual abilities and are episode-linked. The third factor may be amendable to psychosocial treatment.

Cognition Disorders↗