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Biomedical subjects

A Gruber

Publications and source records attributed to A Gruber.

At least 19 recordsLinked to original sources
PubMed2002

Comparison of the genomes of two Xanthomonas pathogens with differing host specificities.

The genus Xanthomonas is a diverse and economically important group of bacterial phytopathogens, belonging to the gamma-subdivision of the Proteobacteria. Xanthomonas axonopodis pv. citri (Xac) causes citrus canker, which affects most commercial citrus cultivars, resulting in significant losses worldwide. Symptoms include canker lesions, leading to abscission of fruit and leaves and general tree decline. Xanthomonas campestris pv. campestris (Xcc) causes black rot, which affects crucifers such as Brassica and Arabidopsis. Symptoms include marginal leaf chlorosis and darkening of vascular tissue, accompanied by extensive wilting and necrosis. Xanthomonas campestris pv. campestris is grown commercially to produce the exopolysaccharide xanthan gum, which is used as a viscosifying and stabilizing agent in many industries. Here we report and compare the complete genome sequences of Xac and Xcc. Their distinct disease phenotypes and host ranges belie a high degree of similarity at the genomic level. More than 80% of genes are shared, and gene order is conserved along most of their respective chromosomes. We identified several groups of strain-specific genes, and on the basis of these groups we propose mechanisms that may explain the differing host specificities and pathogenic processes.

Gene Order↗
PubMed2002

Fibrous meningeal tumours with extensive non-calcifying collagenous whorls and glial fibrillary acidic protein expression: the whorling-sclerosing variant of meningioma.

Meningiomas comprise a wide range of morphological patterns. We describe unusual fibrous meningeal tumours in two patients, composed of extensive non-calcifying collagenous whorls of varying size, resembling non-calcified psammoma bodies, while interposed tumour cells are sparse. Immunohistochemistry showed expression of S-100, vimentin and glial fibrillary acidic protein, whereas only single tumour cells stained for epithelial membrane antigen. Electron microscopy detected desmosomes or desmosome-like structures in both specimens. We conclude that these tumours represent a peculiar whorling-sclerosing variant of fibrous meningioma. Recognition of this meningioma variant is important in the differential diagnosis of meningioma versus other fibrous tumours of the meninges, including solitary fibrous tumours of the meninges, unusual forms of desmoplastic gliomas or chondroid tumours.

Aged↗
PubMed2001

Immature dendritic cells kill ovarian carcinoma cells by a FAS/FASL pathway, enabling them to sensitize tumor-specific CTLs.

Dendritic cells (DCs) can acquire antigen(s) from apoptotic tumor cells, resulting in an immunogen that can induce class I-restricted cytotoxic T lymphocytes (CTLs) and protective tumor rejection. Here, we investigated whether DCs derived from ascitic monocytes of patients with ovarian carcinoma could kill autologous ovarian tumor cells and if as a result they would acquire antigen(s) enabling them to induce a tumor-specific immunity. We found that the immature DCs could exert a significant cytotoxicity towards autologous and allogeneic ovarian tumor cells. This cytotoxicity was independent of Ca(2+) and could be inhibited by anti-Fas IgG1 monoclonal antibody, indicating the involvement of the Fas/Fas ligand (FasL) pathway in the cytotoxic mechanism. Further supporting this conclusion, the ascitic monocyte-derived DCs expressed high levels of FasL mRNA and intracellular FasL and significant levels of Fas were also revealed on the surface of ovarian tumor cells. Coculture of DCs induced apoptosis in ovarian carcinoma cells, as well as uptake of apoptotic tumor cells into the cytoplasma of the DCs, as visualized by immunofluoresence. Autologous DCs cocultured with apoptotic ovarian tumor cells were able to specifically stimulate tumor-specific CTLs, whereas DCs cocultured with necrotic ovarian cells were unable to do so. Collectively, these results demonstrate that immature DCs can kill autologous ovarian carcinoma cells via the Ca(2+)-independent Fas/FasL pathway and that this may have important consequences for their ability to stimulate tumor-specific CTLs.

Antibodies, Monoclonal↗
PubMed2001

Differential effects of HIV-1 protease inhibitors on dendritic cell immunophenotype and function.

Recent findings show that human immunodeficiency virus (HIV)-1 protease inhibitors designed to specifically inhibit the aspartic protease of HIV-1 nonetheless exert various effects on immune cell function in vitro and in vivo. Dendritic cells (DC), central players of the immune system, express several aspartic proteases that are important for DC function. In the present study, we demonstrate that all of the HIV-1 protease inhibitors tested affect DC maturation. In addition, saquinavir had a strong inhibitory effect on the T-cell stimulatory capacity of mature DC. In contrast, indinavir had only a slight effect on DC induced T-cell proliferation and allowed efficient transduction of DC with a replication-incompetent HIV-1 vector designed for DC-based immunotherapy. HIV-1 protease inhibitors that have little or no effect on DC function may be preferable for combination with immunotherapy for HIV/AIDS.

Cell Division↗
PubMed2001

The contribution of 700,000 ORF sequence tags to the definition of the human transcriptome.

Open reading frame expressed sequences tags (ORESTES) differ from conventional ESTs by providing sequence data from the central protein coding portion of transcripts. We generated a total of 696,745 ORESTES sequences from 24 human tissues and used a subset of the data that correspond to a set of 15,095 full-length mRNAs as a means of assessing the efficiency of the strategy and its potential contribution to the definition of the human transcriptome. We estimate that ORESTES sampled over 80% of all highly and moderately expressed, and between 40% and 50% of rarely expressed, human genes. In our most thoroughly sequenced tissue, the breast, the 130,000 ORESTES generated are derived from transcripts from an estimated 70% of all genes expressed in that tissue, with an equally efficient representation of both highly and poorly expressed genes. In this respect, we find that the capacity of the ORESTES strategy both for gene discovery and shotgun transcript sequence generation significantly exceeds that of conventional ESTs. The distribution of ORESTES is such that many human transcripts are now represented by a scaffold of partial sequences distributed along the length of each gene product. The experimental joining of the scaffold components, by reverse transcription-PCR, represents a direct route to transcript finishing that may represent a useful alternative to full-length cDNA cloning.

Expressed Sequence Tags↗
PubMed2001

Cholesterol catabolism in patients with acute myelogenous leukemia and hypocholesterolemia: suppressed levels of a circulating marker for bile acid synthesis.

Hypocholesterolemia is a frequent finding in patients with acute myelogenous leukemia (AML) and in other types of malignancies. Since bile acids are major excretion products of cholesterol, the hepatic degradation of cholesterol to bile acids was investigated in AML patients by analyzing a circulating marker for bile acid synthesis. In addition, plasma levels of a marker for cholesterol synthesis were determined. The plasma levels of 7alpha-hydroxy-4-cholesten-3-one, reflecting bile acid production, were markedly lower in patients with AML than in healthy controls. The median levels were 3.3 and 18.5ng/ml (P<0.0001) in the AML patients (n=29) and the healthy subjects (n=16), respectively. The plasma levels of 7-dehydrocholesterol, reflecting hepatic cholesterol synthesis, were similar for the AML patients and the controls. The results show that the conversion of cholesterol to bile acids was suppressed in AML patients, a phenomenon that may result in a decreased intestinal absorption of cholesterol and subsequent hypocholesterolemia.

Aged↗
PubMed2001

Switch from Myc/Max to Mad1/Max binding and decrease in histone acetylation at the telomerase reverse transcriptase promoter during differentiation of HL60 cells.

Recent evidence suggests that the Myc and Mad1 proteins are implicated in the regulation of the gene encoding the human telomerase reverse transcriptase (hTERT), the catalytic subunit of telomerase. We have analyzed the in vivo interaction between endogenous c-Myc and Mad1 proteins and the hTERT promoter in HL60 cells with the use of the chromatin immunoprecipitation assay. The E-boxes at the hTERT proximal promoter were occupied in vivo by c-Myc in exponentially proliferating HL60 cells but not in cells induced to differentiate by DMSO. In contrast, Mad1 protein was induced and bound to the hTERT promoter in differentiated HL60 cells. Concomitantly, the acetylation of the histones at the promoter was significantly reduced. These data suggest that the reciprocal E-box occupancy by c-Myc and Mad1 is responsible for activation and repression of the hTERT gene in proliferating and differentiated HL60 cells, respectively. Furthermore, the histone deacetylase inhibitor trichostatin A inhibited deacetylation of histones at the hTERT promoter and attenuated the repression of hTERT transcription during HL60 cell differentiation. In addition, trichostatin A treatment activated hTERT transcription in resting human lymphocytes and fibroblasts. Taken together, these results indicate that acetylation/deacetylation of histones is operative in the regulation of hTERT expression.

Acetylation↗
PubMed2001

Telomerase activity in plasma cell dyscrasias.

Activation of telomerase is essential for in vitro cellular immortalization and tumorigenesis. In the present study, we investigated telomerase activation and its implications in plasma cell dyscrasias including monoclonal gammopathy of undetermined significance (MGUS), multiple myeloma (MM) and plasma cell leukaemia (PCL). All 5 patients with MGUS exhibited normal levels of telomerase activity in their plasma cells. Elevated telomerase activity was found in the samples from 21/27 patients with MM and 4/4 with PCL. In addition, 4 myeloma cell lines all expressed high levels of telomerase activity. The expression of telomerase reverse transcriptase (hTERT) and telomerase RNA template (hTER) was positively associated with the levels of telomerase activity in MM/PCL. Tankyrase expression was upregulated, concomitant with the induction of hTERT and activation of telomerase in MM/PCL. The present findings indicate that MGUS cells may not be immortalized and that activation of telomerase plays a role in the malignant transformation from MGUS to MM.

Adult↗
PubMed2001

Intracranial hemorrhage from an aneurysm encased in a pilocytic astrocytoma--case report and review of the literature.

The authors present an unusual complication of a recurrent chiasmal/hypothalamic pilocytic astrocytoma. From his second year of life onwards, the patient was repeatedly operated on and also underwent external radiation therapy (54 Gy total dose) 1 month after the first subtotal tumor resection. Nine years after irradiation, the patient was referred to our center with a sudden onset of severe headache, vomiting and neck stiffness. Computed tomography, magnetic resonance imaging, and cerebral angiography demonstrated an intratumoral, intraventricular, and subarachnoidal hemorrhage from an anterior communicating artery aneurysm encased in the pilocytic astrocytoma. The aneurysm was clipped and the patient recovered nicely from the hemorrhage. Three years later, the patient suddenly died of cardiac failure. Autopsy disclosed vessel wall changes compatible with radiation-induced vasculopathy. In light of this finding, the importance of radiation therapy and intracranial neoplasms for aneurysm formation is discussed.

Acute Disease↗
PubMed2001

In vitro topo II--DNA complex accumulation and cytotoxicity of etoposide in leukaemic cells from patients with acute myelogenous and chronic lymphocytic leukaemia.

Topoisomerase II (topo II) is the target enzyme of etoposide, and DNA--topo II complex accumulation is considered crucial for the cytotoxic effect. We used a SDS--KCl precipitation assay to determine the complex accumulation induced by etoposide in leukaemic cells isolated from 58 patients, 31 with acute myelogenous leukaemia (AML), and 27 with chronic lymphocytic leukaemia (CLL). To investigate whether the sensitivity towards etoposide was dependent on the complex accumulation in the cells, we investigated the drug-induced DNA damage using a DNA unwinding assay and the in vitro cytotoxicity of etoposide using the MTT assay. AML cells had higher complex accumulation (P=0.006) and more DNA damage (P=0.029) compared with CLL cells. The data support a relationship between etoposide-induced complex accumulation and DNA damage in leukaemic cells from AML and CLL patients. However, the induced DNA damage did not translate to in vitro cytotoxicity, suggesting that other factors, such as DNA repair and apoptosis functions, also play important roles to determine the etoposide sensitivity.

Adult↗
PubMed2001

Human immunodeficiency virus type 1 Tat binds to Candida albicans, inducing hyphae but augmenting phagocytosis in vitro.

Tat, the human immunodeficiency virus type 1 (HIV-1) transactivating protein, binds through its RGD-motif to human integrin receptors. Candida albicans, the commonest cause of mucosal candidiasis in subjects infected with HIV-1, also possesses RGD-binding capacity. The present study reveals that Tat binds to C. albicans but not to C. tropicalis. Tat binding was markedly reduced by laminin and to a lesser extent by a complement C3 peptide containing the RGD motif, but not by a control peptide. The outgrowth of C. albicans was accelerated following binding of Tat, but phagocytosis of opsonized C. albicans was also increased after Tat binding. Thus, Tat binding promotes fungal virulence by inducing hyphae but may also reduce it by augmenting phagocytosis. The net effect of Tat in vivo is difficult to judge but in view of the many disease-promoting effects of Tat we propose that accelerating the formation of hyphae dominates over the augmentation of phagocytosis.

ATPases Associated with Diverse Cellular Activitie↗
PubMed2001

Activation of pro-astacin. Immunological and model peptide studies on the processing of immature astacin, a zinc-endopeptidase from the crayfish Astacus astacus.

To contribute knowledge of the processing and activation of invertebrate proteolytic enzymes, we studied the metalloprotease astacin, a digestive enzyme from the freshwater crayfish Astacus astacus (decapod crustacean). It is the prototype of the protein family of astacins, members of which occur in organisms from bacteria to man and are involved in a variety of physiological reactions. According to its genomic structure, astacin is produced as a zymogen [Geier, G., Jacob, E., Stöcker, W. & Zwilling, R. (1997) Arch. Biochem. Biophys. 337, 300-307]. To localize and follow the processing of pro-astacin in different parts of the digestive tract, we synthesized two peptides covering the pro part of pro-astacin and raised antibodies against them. In addition, antiserum against the whole active astacin was produced. Using immunohistochemical investigation, we detected pro-astacin in the F cells of the hepatopancreas and all the way into the tubular lumen and the collecting ducts of this gland. Immunoblot assays revealed only active astacin, and never pro-astacin, present in the cardiac stomach. We conclude from these studies that astacin is secreted into the lumen of the hepatopancreatic tubules in its pro form and is activated on its way to the stomach. To investigate which of the two endopeptidases found in the digestive tract of crayfish, astacin or trypsin, is responsible for cleaving the propeptide from pro-astacin, we synthesized different peptides that mimick the activation site. MS analysis of the cleavage products of astacin and trypsin showed that astacin is capable of catalyzing its own activation. Any contribution of trypsin would require the successive action of an aminopeptidase. Substituting glycine for arginine at position -1 of the activation site does not prevent astacin activity. As most members of the astacin protein family have basic amino-acid residues in this position, in these cases also astacin-specific cleavage would be possible.

Amino Acid Sequence↗
PubMed2001

Compactotomy in Huntington's chorea.

Advances in neuroradiological and neurosurgical techniques have lead to a growing interest in functional neurosurgical interventions for medically intractable movement disorders. The majority of these procedures are performed in patients with hypokinetic movement disorders, especially Parkinson's disease. However, relatively few interventions were done in hyperkinetic disorders such as Huntington's disease (HD), mainly owing to the lack of an adequate target nucleus. We have recently described the case of a reversible chorea in a genetically confirmed HD patient. We subsequently identified a marked bilateral degeneration of the substantia nigra as the probable reason for choreatic cessation. We therefore suggest that primary striatal atrophy causing hyperkinesia and secondary substantia nigra atrophy favouring hypokinesia were balanced in this patient, thus resulting in a close-to-physiologic GABAergic basal ganglia output. We postulate that deep brain stimulation of the substantia nigra pars compacta may ameliorate hyperkinesia in choreatic movement disorders, thus representing the first effective therapy in Huntington's chorea. Several lines of evidence in recent neurophysiological research support our hypothesis and are discussed below.

Humans↗
PubMed2001

Real-time quantitative telomeric repeat amplification protocol assay for the detection of telomerase activity.

BACKGROUND: Telomerase is a ribonucleoprotein enzyme associated with immortalization and transformation of human cells. The telomeric repeat amplification protocol (TRAP) is widely used for the detection of telomerase activity. The TRAP method, although highly sensitive and specific because it includes PCR amplification, is laborious and does not provide precise quantitative information. METHODS: We developed a real-time quantitative TRAP (RTQ-TRAP) system by combining a real-time PCR technique with the conventional TRAP method. Telomerase activity in human tumor cell lines and in 13 lymphoma samples was measured using the RTQ-TRAP assay, and the results obtained from the samples using the RTQ-TRAP method were compared with the conventional TRAP method. RESULTS: The RTQ-TRAP method was both accurate and reproducible in measuring telomerase activity in a dilution series of protein extracts from HL60 cells. Telomerase activity in 13 lymphoma samples, as determined by the RTQ-TRAP method, was ninefold lower than that measured by the conventional TRAP method. The half-life of telomerase activity in human tumor cells, as determined using RTQ-TRAP, was much shorter than the half-life reported previously. CONCLUSIONS: Our results suggest that the conventional TRAP assay frequently overestimates telomerase activity in tumor samples. The RTQ-TRAP method is thus a useful tool to rapidly and precisely quantify telomerase activity.

Enzyme-Linked Immunosorbent Assay↗
PubMed2001

Telomerase activity in relation to pro- and anti-apoptotic protein expression in high grade non-Hodgkin's lymphomas.

BACKGROUND AND OBJECTIVES: Telomerase activity (TA) is determined by the catalytic unit telomerase reverse transcriptase (hTERT). In vitro studies show that hTERT is downregulated by wild type p53 and TA is upregulated by BCL-2 expression. The aim of this study was to investigate the relationship of TA and mRNA expression of hTERT, telomerase RNA (hTER) and Tankyrase in 31 samples from patients with high-grade non-Hodgkin's lymphoma (HG-NHL). The results were then related to apoptosis and proliferation and the expression of p53 and BCL-2 family member proteins. DESIGN AND METHODS: The telomeric repeat amplification protocol (TRAP) assay and reverse transcription-polymerase chain reaction (RT-PCR) were used to quantify TA, and hTERT, hTER and Tankyrase mRNA expression. Proliferation (Ki67), p53, BCL-2, MCL-1, BAX and BAK protein expression were evaluated by immunohistochemistry. Apoptosis was evaluated by TUNEL staining. RESULTS: TA was detected in 93% of HG-NHL and tended to be higher in p53+ lymphomas. A positive correlation existed between mRNA expression of hTERT, hTER and Tankyrase. hTERT mRNA expression tended to be higher with increasing levels of apoptosis and proliferation, in HG-NHL samples lacking BAX expression and in samples from patients with survival shorter than 3.5 years. hTER mRNA expression was significantly higher in BAX and BAK negative samples. INTERPRETATION AND CONCLUSIONS: Telomerase is activated or upregulated in the majority of HG-NHL. Enhanced TA combined with deregulation of the factors responsible for cell survival and proliferation may contribute to the development and progression of lymphomas. Observation that high hTERT mRNA expression may be related to shorter survival should prompt further investigation of the clinical significance of TA and its components in HG-NHL.

Adult↗