Biomedical subjects

A Gruber

Publications and source records attributed to A Gruber.

At least 55 records · Page 3Linked to original sources

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↗

PubMed2000

Interferon alpha down-regulates telomerase reverse transcriptase and telomerase activity in human malignant and nonmalignant hematopoietic cells.

Recently, the derepressed expression of the catalytic subunit of telomerase, human telomerase reverse transcriptase (hTERT), the enzyme that elongates telomeres, has been implicated as an important step in the immortalization process. The exact regulation of hTERT expression, which is the rate-limiting factor for telomerase activity, is at present unclear. As transformed cells seem to be dependent on a constitutive telomerase activity, the availability of inhibitors would potentially be of great value in antineoplastic therapy. Interferons (IFNs) have been successfully used in the treatment of several forms of malignancies, but the underlying molecular mechanisms responsible for the antitumor activity are poorly defined. In this study we have investigated the effects of IFNs on hTERT expression and telomerase activity. We found that IFN-alpha rapidly (commonly within 4 hours) and significantly down-regulates the expression of hTERT and telomerase activity in a number of human malignant hematopoietic cell lines, primary leukemic cells from patients with acute leukemia as well as T-lymphocytes from healthy donors. This effect of IFN-alpha did not seem to depend on IFN-alpha-mediated cell growth arrest or alterations in c-myc expression. The finding that IFN induces a repression of hTERT and a decrease in telomerase activity suggests a novel mechanism that may play a significant role in the antitumor action of IFN. (Blood. 2000;96:4313-4318)

Acute Disease↗

PubMed2000

Frequent amplification of the telomerase reverse transcriptase gene in human tumors.

Activation of telomerase is a crucial step during cellular immortalization and malignant transformation of human cells and requires the induction of the catalytic component, human telomerase reverse transcriptase (hTERT), encoded by the hTERT gene. It is poorly understood how the hTERT gene is activated in human cancer cells. In the present study, we examined the hTERT gene copy number in human cancer cell lines and in primary tumor tissues. Amplification of the hTERT gene was observed in 8 of 26 (31%) tumor cell lines and 17 of 58 (30%) primary tumors examined (8 of 21 lung tumors, 3 of 10 cervical tumors, 5 of 19 breast carcinomas, and 1 of 8 neuroblastomas). In addition, 13 of 26 (50%) cell lines and 13 of 58 (22%) primary tumors displayed gain of hTERT gene copies with 3-4 copies/cell. The present findings imply that the hTERT locus may be a frequent target for amplification during tumorigenesis and that this genetic event probably contributes to the dysregulation of telomerase activity occurring in human tumors.

Catalytic Domain↗

PubMed2000

Identification of human chromosome 22 transcribed sequences with ORF expressed sequence tags.

Transcribed sequences in the human genome can be identified with confidence only by alignment with sequences derived from cDNAs synthesized from naturally occurring mRNAs. We constructed a set of 250,000 cDNAs that represent partial expressed gene sequences and that are biased toward the central coding regions of the resulting transcripts. They are termed ORF expressed sequence tags (ORESTES). The 250,000 ORESTES were assembled into 81,429 contigs. Of these, 1, 181 (1.45%) were found to match sequences in chromosome 22 with at least one ORESTES contig for 162 (65.6%) of the 247 known genes, for 67 (44.6%) of the 150 related genes, and for 45 of the 148 (30.4%) EST-predicted genes on this chromosome. Using a set of stringent criteria to validate our sequences, we identified a further 219 previously unannotated transcribed sequences on chromosome 22. Of these, 171 were in fact also defined by EST or full length cDNA sequences available in GenBank but not utilized in the initial annotation of the first human chromosome sequence. Thus despite representing less than 15% of all expressed human sequences in the public databases at the time of the present analysis, ORESTES sequences defined 48 transcribed sequences on chromosome 22 not defined by other sequences. All of the transcribed sequences defined by ORESTES coincided with DNA regions predicted as encoding exons by genscan. (http://genes.mit.edu/GENSCAN.html).

Chromosomes, Human, Pair 22↗

PubMed2000

Downregulation of telomerase reverse transcriptase mRNA expression by wild type p53 in human tumor cells.

The p53 tumor suppressor protein inhibits the formation of tumors through induction of cell cycle arrest and/or apoptosis. In the present study we demonstrated that p53 is also a powerful inhibitor of human telomerase reverse transcriptase (hTERT), a key component for telomerase. Activation of either exogenous temperature-sensitive (ts) p53 in BL41 Burkitt lymphoma cells or endogenous wild type (wt) p53 at a physiological level in MCF-7 breast carcinoma cells triggered a rapid downregulation of hTERT mRNA expression, independently of the induction of the p53 target gene p21. Co-transfection of an hTERT promoter construct with wt p53 but not mutant p53 in HeLa cells inhibited the hTERT promoter activity. Furthermore, the activation of the hTERT promoter in Drosophila Schneider SL2 cells was completely dependent on the ectopic expression of Sp1 and was abrogated by wt p53. Finally, wt p53 inhibited Sp1 binding to the hTERT proximal promoter by forming a p53-Sp1 complex. Since activation of telomerase, widely observed in human tumor cell lines and primary tumors, is a critical step in tumorigenesis, wt p53-triggered inhibition of hTERT/telomerase expression may reflect yet another mechanism of p53-mediated tumor suppression. Our findings provide new insights into both the biological function of p53 and the regulation of hTERT/telomerase expression.

Breast Neoplasms↗

PubMed2000

Dendritic cells transduced by multiply deleted HIV-1 vectors exhibit normal phenotypes and functions and elicit an HIV-specific cytotoxic T-lymphocyte response in vitro.

Dendritic cells (DCs) genetically modified to continually express and present antigens may be potent physiologic adjuvants for induction of prophylactic or therapeutic immunity. We have previously shown that an env and nef deleted HIV-1 vector (HIV-1 delta EN) pseudotyped with VSV-G transduced monocyte-derived macrophages as well as CD34(+) precursors of DCs. Here we extended these findings with HIV-1 delta EN to highly differentiated human DCs derived in culture from circulating monocytes (DCs). In addition, a new vector derived from HIV-1 delta EN but further deleted in its remaining accessory genes vif, vpr, and vpu (HIV-1 delta EN V(3)) was also tested. Both vectors efficiently transduced DCs. Transduction of DCs did not significantly alter their viability or their immunophenotype when compared with untransduced DCs. Furthermore, the phagocytic potential of immature DCs, as well as their ability to differentiate into mature DCs capable of stimulating T-cell proliferation, was not affected. Finally, DCs transduced by the HIV-1 delta EN vector were able to elicit a primary antiviral cytotoxic T-cell response in autologous CD8 T cells. These results suggest that HIV-1-based vectors expressing viral antigens may be useful for in vivo active immunization as well as ex vivo priming of cytotoxic T cells for adoptive T-cell therapy. (Blood. 2000;96:1327-1333)

Acquired Immunodeficiency Syndrome↗

PubMed2000

The genome sequence of the plant pathogen Xylella fastidiosa. The Xylella fastidiosa Consortium of the Organization for Nucleotide Sequencing and Analysis.

Xylella fastidiosa is a fastidious, xylem-limited bacterium that causes a range of economically important plant diseases. Here we report the complete genome sequence of X. fastidiosa clone 9a5c, which causes citrus variegated chlorosis--a serious disease of orange trees. The genome comprises a 52.7% GC-rich 2,679,305-base-pair (bp) circular chromosome and two plasmids of 51,158 bp and 1,285 bp. We can assign putative functions to 47% of the 2,904 predicted coding regions. Efficient metabolic functions are predicted, with sugars as the principal energy and carbon source, supporting existence in the nutrient-poor xylem sap. The mechanisms associated with pathogenicity and virulence involve toxins, antibiotics and ion sequestration systems, as well as bacterium-bacterium and bacterium-host interactions mediated by a range of proteins. Orthologues of some of these proteins have only been identified in animal and human pathogens; their presence in X. fastidiosa indicates that the molecular basis for bacterial pathogenicity is both conserved and independent of host. At least 83 genes are bacteriophage-derived and include virulence-associated genes from other bacteria, providing direct evidence of phage-mediated horizontal gene transfer.

Bacterial Adhesion↗

PubMed2000

Evaluation of big endothelin-1 concentrations in serum and ventricular cerebrospinal fluid after early surgical compared with nonsurgical management of ruptured intracranial aneurysms.

OBJECT: Whereas the removal of subarachnoid blood is possible during early-stage aneurysm surgery, this cannot be achieved in aneurysms treated by endovascular means. The levels of potential spasmogens in the cerebrospinal fluid (CSF) in patients receiving endovascular treatment might therefore be higher, with the potential for more severe post-subarachnoid hemorrhage (SAH) vasospasm. METHODS: Serum and CSF concentrations of big endothelin (ET)-1 were serially measured in patients with SAH receiving one of the following treatments: 1) early (within 72 hours of SAH) aneurysm surgical treatment (15 patients), 2) early endovascular treatment (17 patients), or 3) no intervention in the acute phase (12 patients). In patients suffering delayed infarctions higher levels of big ET-1 CSF were demonstrated than in those without infarctions (p = 0.01). In patients in whom surgery was performed in the acute phase lower big ET-1 CSF concentrations were demonstrated than in those who received embolization treatment or no treatment (p = 0.02). Subgroup analysis demonstrated that in patients receiving early endovascular treatment, higher big ET-1 CSF concentrations were revealed than in those undergoing early aneurysm surgery; this was true for patients with (microsurgerytreated, 1.84 +/- 0.83 pg/ml; and embolization-treated 2.19 +/- 0.54 pg/ml) and without (microsurgery-treated 1.76 +/- 0.61 pg/ml; and embolization-treated 2.01 +/- 0.48 pg/ml) delayed infarctions. CONCLUSIONS: Among patients with SAH who received treatment during the acute phase, those undergoing early aneurysm surgery were shown to have lower big ET-1 CSF levels than those receiving embolization and no treatment (that is, the nonsurgical treatment groups). The clinical significance of this finding remains to be established in future clinical trials, because in the present study the trend toward lower levels of big ET-1 CSF in the microsurgically treated group was not paralleled by a lower delayed stroke rate or an improvement in neurological outcome.

Adult↗

PubMed2000

Histamine suppresses neopterin production in the human myelomonocytoma cell line THP-1.

Histamine, an important inflammatory mediator in allergic diseases and asthma, was reported to have modulatory effects on T cells by down-regulating Th1-type cell cytokines like interleukin 2 (IL-2) and interferon-gamma (IFN-gamma). In this study we examined the effect of histamine and the histamine-receptor antagonists cimetidine and diphenhydramine on the production of neopterin after stimulation with IFN-gamma in the myelomonocytoma cell line THP-1. Increasing concentrations of histamine markedly suppressed IFN-gamma induced neopterin formation. Simultaneous preincubation of THP-1 cells with histamine, IFN-gamma and different concentrations of the H(2)-receptor antagonist cimetidine showed a clear antagonizing effect on neopterin formation. In contrast, the H(1)-receptor antagonist diphenhydramine was not able to abrogate the suppressive effect of histamine on neopterin production. Our results suggest, that histamine may be a potent inhibitor of effects or mechanisms induced by IFN-gamma in monocytes/macrophages. Cimetidine, and possibly other H(2)-receptor antagonists, may reverse down-regulatory actions of endogenously formed histamine on activated monocytic cells.

Adjuvants, Immunologic↗

PubMed2000

Intra-arterial thrombolysis for the treatment of perioperative childhood cardioembolic stroke.

Local intra-arterial lysis using recombinant tissue plasminogen activator (rTPA) was performed in a 6 and 2/3-year-old patient with major cardioembolic ischemic stroke 48 hours after intracardiac surgery. Selective application of 2.5 mg rTPA (0.11 mg/kg body weight) resulted in recanalization of the occluded cerebral vasculature with good neurologic recovery.

Cardiac Surgical Procedures↗

PubMed2000

Preoperative embolization of hypervascular skull base tumors.

The purpose of the present study is to review the results and complications of preoperative embolization of hypervascular skull base tumors at a neurosurgical center with a team of neurosurgeons cross-experienced in the application of both microsurgery and endovascular techniques. One hundred and twenty-eight endovascular approaches were performed in 66 patients treated for skull base meningiomas (n = 41), paragangliomas of the temporal bone (n = 18), and juvenile nasopharyngeal angiofibromas (n = 7). One death and 2 permanent disabilities were attributable to endovascular therapy. These complications occurred early in our experience (1982-1989) and were related to thromboembolic events rather than complications of transcatheter embolization itself. Our current standard is to perform transfemoral superselective embolizations with either finely corpuscular embolizing substances (PVA particles) or cyanoacrylates (NBCA) under local anesthesia. Using this protocol no embolization-related complications have occurred over the last 9 years. We thus conclude that preoperative embolization of hypervascular skull base tumors can be accomplished safely with the endovascular techniques now available.

Adult↗

PubMed2000

Preoperative embolization of intracranial meningiomas: a 17-years single center experience.

The purpose of the present report is to review the evolution of endovascular therapy at our center as utilized for the preoperative embolization of intracranial meningiomas over a 17-years period (1982-1998). This study is based upon a consecutive series of 63 patients who underwent preoperative embolization of intracranial meningiomas. Total or subtotal angiographic devascularization of the tumor parenchyma was accomplished in 38 patients (60.3%) who had tumors with either an external carotid artery supply only (n = 30) or with contributions from the cavernous carotid artery, ophthalmic artery, vertebral artery, or pial feeders which were feasible for selective embolization (n = 8). Partial tumor embolizations were attained in the remaining 25 patients (39.7%) because 1. the remanent feeders were considered easily accessible to surgical control in the early stages of dissection, 2. the feeding branches were inaccessible for a microcatheter approach, or 3. superselective microcatheter positions allowing for safe embolization without reflux of embolic material into physiological branches were not achieved. Overall, 97 of 126 tumor feeders identified angiographically were catheterized to selective embolization (77%). Three embolization related complications occurred early in our experience (1982-1989) using techniques which no longer meet standards of treatment. In light of the remarkable evolution of endovascular techniques over the 17-years study period, however, we conclude that preoperative embolization of intracranial meningiomas can be performed safely with the endovascular tools currently available.

Adult↗

PubMed2000

Prior sensitization of esophageal mucosa by acid reflux predisposes to reflux-induced chest pain.

Esophageal acid exposure is believed to be a major source of unexplained chest pain; but, individual episodes of reflux in pH study are not consistently associated with chest pain. Our aim was to discover whether prior sensitization of esophageal mucosa by acid reflux predisposes to reflux-induced chest pain. Ambulatory pH studies of patients referred to our laboratory from January 1991 to November 1996 with noncardiac chest pain was reviewed. We compared the frequency of esophageal acid exposure in the 30 minutes preceding chest pain episodes with a positive symptom/reflux association (+SRA) to reflux with the frequency of acid exposure in the 30 minutes preceding those chest pain episodes that were not associated with reflux negative symptom/reflux association (-SRA). We analyzed the time esophageal pH <4, symptom index (SI) defined as percentage of chest pain episodes associated with reflux in the preceding 5 minutes, and amount of reflux in the 30 minutes preceding each chest pain episode. Of 104 patients, 52 had chest pain during their pH study, 10 had high SI (> or =50%), and 42 had low SI (<50%). Those with a high SI were significantly more likely to have an abnormal pH study (p = 0.015). Chest pain associated with reflux in proceeding 5 minutes (+SRA) was strongly associated (p < 0.002) with additional reflux episodes in the preceding 25-minute period. Chest pain related to reflux is associated with sensitization of the esophageal mucosa by prior reflux events.

Adult↗

PubMed2000

Ventricular cerebrospinal fluid and serum concentrations of sTNFR-I, IL-1ra, and IL-6 after aneurysmal subarachnoid hemorrhage.

Postsubarachnoid hemorrhage, systemic inflammatory response syndrome and associated organ system failure are more frequently found in patients in poor neurologic condition. Since subarachnoid hemorrhage causes a profound intrathecal inflammatory response with production of proinflammatory cytokines TNFalpha, IL-1beta, and IL-6, a possible explanation for this association is that brain-derived cytokines may enter the systemic circulation in the presence of postsubarachnoid hemorrhage blood brain barrier disruption to systemically activate inflammatory cascades and thereby contribute to the development of postsubarachnoid hemorrhage systemic inflammatory response syndrome and extracerebral organ system failures. In 44 patients with aneurysmal subarachnoid hemorrhage admitted within 3 days of the initial bleed, extracerebral organ system functions were assessed individually and in aggregate using the modified Multiple Organ Dysfunction Score. Serum and cerebrospinal fluid concentrations of soluble tumor necrosis factor-alpha receptor-I, interleukin-1beta receptor antagonist, and IL-6 were determined during the first 2 weeks after subarachnoid hemorrhage and tested for correlation with (1) admission Hunt-Hess grade, (2) development of systemic inflammatory response syndrome and extracerebral organ system failures, and (3) neurologic outcome. The development of postsubarachnoid hemorrhage systemic inflammatory response syndrome and extracerebral organ system failures was paralleled by a significant increase in serum but not in cerebrospinal fluid levels of soluble tumor necrosis factor-alpha receptor-I and IL-1ra, that is, patients with and without extracerebral organ system failures did not differ in pattern and time course of cerebrospinal fluid cytokine concentrations. In contrast, increasing soluble tumor necrosis factor-alpha receptor-I and interleukin-1beta receptor antagonist serum levels correlated with a higher Multiple Organ Dysfunction score and with individual organ system dysfunctions. Postsubarachnoid hemorrhage, systemic inflammatory response syndrome and extracerebral organ system failures could therefore not be linked to changes in cerebrospinal fluid cytokine concentration profiles.

Adult↗

PubMed2000

Membrane attack complex formation on yeast as trigger of selective release of terminal complement proteins from human polymorphonuclear leukocytes.

It has recently been shown that measurable amounts of complement proteins, C6 and in particular C7, are released from human polymorphonuclear leukocytes (PMNs). The aim of the present study was to investigate the impact of opsonized Candida albicans on this release. Stimulation with opsonized C. albicans led to a rapid and sustained increase of C6 and C7 in the cell culture supernatant beginning within 5 min of placing in co-culture, whereas co-culture with unopsonized C. albicans or C. albicans mock-opsonized with inactivated human serum did not affect the release. In contrast, even after stimulation employing opsonized C. albicans, no release of the complement component C8 and only trace amounts of C9 were detected. The presence of the membrane attack complex (MAC) on C. albicans after opsonization was demonstrated by indirect immunofluorescence. Opsonization of C. albicans with human serum deficient in or depleted of a terminal complement component resulted in only minor stimulation of C6 and C7 release, although C3 deposition on the surface of C. albicans was not affected as determined by direct immunofluorescence. Detailed analyses with inactivated or deficient sera showed that detection of C6 and C7 was not due to insufficient washing of the opsonized yeast prior to co-culture and suggest that only a small proportion of these proteins was derived from the membrane bound and then cleaved off MAC. Thus, these findings imply that MAC on the fungal surface may represent an additional trigger for the release of C6 and C7 from PMNs, suggesting a new role for the terminal complement complex (TCC) on target membranes as modulator of PMN functions locally at the site of inflammation.

Candida↗

PubMed2000

Bioavailability of aciclovir after oral administration of aciclovir and its prodrug valaciclovir to patients with leukopenia after chemotherapy.

The median bioavailabilities of aciclovir after administration of aciclovir and its prodrug valaciclovir were 21.5 and 70.1%, respectively, in 12 patients with malignant hematological diseases with leukopenia after chemotherapy. The interindividual variations of the bioavailability were 48.5 and 21.0% after administration of aciclovir and valaciclovir, respectively. Neither the bioavailability nor the interindividual variation of area under the concentration-time curve of oral aciclovir or valaciclovir differed from that reported in healthy volunteers.

Acyclovir↗

PubMed2000

P-Glycoprotein inhibitor valspodar (PSC 833) increases the intracellular concentrations of daunorubicin in vivo in patients with P-glycoprotein-positive acute myeloid leukemia.

PURPOSE: The aim of the present study was to evaluate the effect of the cyclosporine derivative valspodar (PSC 833; Amdray, Novartis Pharma, Basel, Switzerland) on the concentration of daunorubicin (dnr) in leukemic blast cells in vivo during treatment. PATIENTS AND METHODS: Ten patients with acute myeloid leukemia (AML) were included. Leukemic cells from seven of the patients were P-glycoprotein (Pgp)-positive. dnr 100 mg/m(2) was given as a continuous infusion over 72 hours. After 24 hours, a loading dose of valspodar was given, followed by a 36-hour infusion of 10 mg/kg per 24 hours. Blood samples were drawn at regular intervals, and concentrations of dnr and its main metabolite, daunorubicinol, in plasma and isolated leukemic cells were determined by high-pressure liquid chromatography. RESULTS: The mean dnr concentrations in leukemic cells 24 hours after the start of infusion (before valspodar) were 18.8 micromol/L in Pgp-negative samples and 13.5 micromol/L in Pgp-positive samples. After 8 hours of valspodar infusion, these values were 25.8 and 24.0 micromol/L, respectively. The effect of valspodar was evaluated from the ratio of the area under the curve (AUC) for dnr concentration versus time in leukemic cells to the AUC for dnr concentration against time in the plasma. For the seven patients with Pgp-positive leukemia, the mean ratio increased by 52%, from 545 on day 1 to 830 on day 2 (P<.05) when valspodar was given. In the three patients with Pgp-negative leukemia, no significant difference was observed. CONCLUSION: These results strongly suggest that valspodar, by interacting with Pgp, can increase the cellular uptake of dnr in leukemic blasts in vivo.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2000

De novo formation and rupture of an azygos pericallosal artery aneurysm. Case report.

An azygos pericallosal artery (APCA) aneurysm is a rare anomaly that is closely associated with saccular aneurysms. This is the earliest report to document de novo formation and rupture of an aneurysm at the bifurcation of an unpaired pericallosal trunk. The authors report the case of a woman who presented at the age of 52 years with subarachnoid hemorrhage (SAH) from the rupture of a newly formed APCA bifurcation aneurysm, 7 years after she had undergone surgery to clip a ruptured anterior cerebral artery aneurysm. De novo formation of aneurysms after SAH rarely occurs and certain risk factors like multiple and familial aneurysms, arterial hypertension, or smoking have been postulated. Late follow-up examination with angiography to detect de novo aneurysms should be considered in patients with this vascular anomaly after SAH.

Aneurysm, Ruptured↗