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G Bruchelt

Publications and source records attributed to G Bruchelt.

At least 55 records · Page 3Linked to original sources
PubMed1991

Isotachophoretic determination of 2-5A phosphodiesterase.

Together with 2-5A synthetase and ribonuclease L, 2-5A phosphodiesterase belongs to the 2-5A system, which plays an important role in the action of interferon. Analytical capillary isotachophoresis was used for the determination of 2-5A phosphodiesterase activity. Enzyme assay was optimized using snake venom phosphodiesterase as a source of 2-5A phosphodiesterase activity. The 2-5A trimer core was used as a substrate. Enzyme activity was determined in time- and concentration-dependent reactions. In addition, 2-5A phosphodiesterase activity was determined in lysates of mononuclear blood cells.

Adenine Nucleotides↗
PubMed1990

Reduction of N-myc expression by antisense RNA is amplified by interferon: possible involvement of the 2-5A system.

Expression of myc-box genes can be reduced by Interferon (c-myc in Daudi cells) or Retinoic acid (N-myc in neuroblastoma cells). Interferon did not reduce N-myc expression in neuroblastoma cells. However, after transfection of the human neuroblastoma cell line LS with a vector, providing the Cadmium inducible expression of an antisense N-myc transcript, drastic reduction of N-myc RNA was achieved in these cells by incubation with Cadmium and Interferon. Treatment with Cadmium alone resulted in a comparably small reduction of N-myc transcripts in these cells. Interferon alone did not appreciably affect N-myc expression. Reduction of N-myc was accompanied with reduced cell proliferation and morphological differentiation. It is assumed that most of the inhibitory effects observed are mediated by the Interferon inducible 2-5A system.

2',5'-Oligoadenylate Synthetase↗
PubMed1990

Vasoactive intestinal polypeptide (VIP) induces calcium mobilization in the human neuroblastoma cell line SK-N-SH.

Release of catecholamines, a Ca2(+)-dependent process, is the most useful biochemical marker in the diagnosis of neuroblastoma. Unfortunately, its stimulus is still unknown. We found that vasoactive intestinal polypeptide (VIP), in addition to acetylcholine and muscarine (but not nicotine), causes elevation of the cytoplasmic Ca2(+)-concentration in the highly differentiated human neuroblastoma cell line SK-N-SH, with or without the presence of extracellular Ca2+. Additionally, VIP was detected in SK-N-SH cells (0.65 ng/10(6) cells). Based on these observations and the fact that neuroblastoma is not innervated in vivo, we hypothesize that in this tumor VIP is responsible for Ca2(+)-dependent release of catecholamines in an autocrine or paracrine fashion.

Acetylcholine↗
PubMed1990

In vitro and in vivo effect of interleukin-2 on the 2',5'-oligoadenylate synthetase activity of peripheral mononuclear blood cells.

The in vitro and in vivo influence of interleukin-2 (IL-2) on 2',5'-oligoadenylate (2-5A) synthetase activity and natural killer (NK) activity of peripheral mononuclear blood cells (PBMCs) was investigated. Incubation of PBMCs in vitro with IL-2 resulted in a considerable secretion of interferon-gamma (IFN-gamma) and in a significant elevation of 2-5A synthetase activity, as well as NK activity. Neutralizing monoclonal anti-IFN-gamma antibodies inhibited the elevation of 2-5A synthetase activity, but not the IL-2-induced augmentation of NK activity. Additionally, 2-5A synthetase and NK activity of PBMCs was measured in a child with neuroblastoma that was treated with recombinant IL-2 by continuous intravenous application. During the treatment, NK activity against the NK-sensitive cell line K 562 and against autologous tumor cells was not augmented. However, a significant increase of 2-5A synthetase activity in PBMCs was observed during IL-2 treatment, whereas there was no detectable serum level of IFN-gamma. We conclude that measuring 2-5A synthetase activity in patients treated with IL-2 may be helpful in monitoring the immunomodulatory effects of IL-2 on immune effector cells.

2',5'-Oligoadenylate Synthetase↗
PubMed1990

Release of iron from ferritin by 6-hydroxydopamine under aerobic and anaerobic conditions.

6-hydroxydopamine (6-OHDA) proved to be a very effective agent for iron release from ferritin. Iron release was enhanced in the presence of SOD, catalase and under anaerobic conditions. Ascorbic acid, a well known agent able to release iron from ferritin, increased the amount of released iron in more than an additive manner when used in combination with 6-OHDA. Similar to 6-OHDA, 6-hydroxydopa (Topa) and 1,2,4-benzenetriol were also able to release iron in large amounts; in contrast, catecholamines and other benzenediols were comparatively ineffective.

Aerobiosis↗
PubMed1989

Investigations on the interferon-induced 2'-5' oligoadenylate system using analytical capillary isotachophoresis.

The activity of the interferon inducible enzyme 2'-5' oligoadenylate synthetase (2-5A synthetase, E.C. 2.7.7) which converts ATP into a series of 2'-5' oligoadenylates was measured using analytical capillary isotachophoresis. The turnover rate of ATP during the reaction was monitored by determination of its concentration at the beginning and the end of the 2-5A synthetase reaction. The enzyme was analysed in extracts of peripheral blood mononuclear cells either pretreated or not with interferon.

2',5'-Oligoadenylate Synthetase↗
PubMed1989

Lysis of neuroblastoma cells by the ADCC-reaction: granulocytes of patients with chronic granulomatous disease are more effective than those of healthy donors.

Granulocytes from healthy donors lyse human neuroblastoma cells in the ADCC-reaction using antibody MAb 14.18 directed to ganglioside GD2 present on the surface of most neuroblastoma cells. Addition of catalase, superoxide dismutase and azide do not impair this process. Granulocytes from patients with chronic granulomatous disease (CGD) kill neuroblastoma cells even better than those collected from healthy donors. These results indicate that reactive oxygen intermediates (ROI) are not involved in killing of neuroblastoma cells using MAb 14.18, and that granulocytes from patients with CGD may compensate for defects in generation of reactive oxygen intermediates by more effective oxygen-independent killing mechanisms. One patient with CGD was treated with interferon-gamma. During and after treatment, generation of ROI could not be detected and neuroblastoma cell killing was not significantly altered.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1989

In vitro induction of lymphokine-activated killer (LAK) activity in patients with neuroblastoma.

Therapy of disseminated neuroblastoma remains an unsolved problem in pediatric oncology. Therefore, new therapeutic approaches have to be developed for this malignancy. In this paper, we investigated the possibility of the in vitro generation and expansion of lymphokine-activated killer (LAK) cells in patients with disseminated neuroblastoma. Although the patients had very low Natural Killer (NK) activity, it was possible to induce LAK activity in peripheral mononuclear lymphocytes (PMNC) by incubation with Interleukin-2 (IL-2). Moreover, the PMNCs could be expanded up to 50-fold in the presence of Interleukin-2 while maintaining or even increasing their LAK activity. The target cells were neuroblastoma cell lines and, in one case, autologous neuroblastoma cells. Additionally, it was possible to induce LAK cell activity against autologous neuroblastoma cells in bone marrow-derived mononuclear cells.

Bone Marrow↗
PubMed1989

Cytotoxic effects of 6-hydroxydopamine, merocyanine-540 and related compounds on human neuroblastoma and hematopoietic stem cells.

6-Hydroxydopamine(6-OHDA) and Merocyanine-540(MC-540) have been used clinically for purging of neuroblastoma cells prior to autologous bone marrow transplantation. Both substances were found to be more toxic against neuroblastoma cells than against hematopoietic stem cells. The more pronounced cytotoxic effects of 6-OHDA against neuroblastoma cells were not caused by its selective uptake; the rapid autooxidation at physiological pH leads to the formation of H2O2 already in the incubation medium. Cytotoxic effects were not detected in short-time test systems (4 hour chromium-51 release assay) but only after longer incubation periods. In contrast, MC-540 proved to be toxic almost equally in short- and long-time test systems. 4-Hydroxynonenal(4-HNE) that may be formed in the plasma membrane subsequently to photoactivation of MC-540 was only slightly more toxic to neuroblastoma cells than to hematopoietic cells. Although the use of 6-OHDA and MC-540 in bone marrow purging has some limitations, the sensitivity of neuroblastoma cells against reactive oxygen compounds may be exploited more generally for therapy of this tumor.

Aldehydes↗
PubMed1989

Bone marrow transplantation in children with neuroblastoma.

Neuroblastoma is the third most frequent malignant tumor in childhood. One-third of the patients over one year of age at the time of diagnosis suffer from the disseminated form (stage IV). Despite highly aggressive chemotherapy survival rates are poor. One hundred and eighty-seven patients with neuroblastoma stage IV have been treated according to the German protocol NB 85. The probability of disease free survival is only 15% after 70 months. Treatment strategy in our protocol includes autologous and allogeneic bone marrow transplantation (BMT) for patients with stage IV (and greater than 1 year old). Twenty-two patients were grafted (7 allogeneic and 15 autologous). The conditioning regimen consisted mainly of high-dose melphalan (180 mg/m2) and total body irradiation (TBI) (3.4 Gy). Survival rates are discussed in the context of the chemotherapy protocol. Our own experience with autologous BMT is poor, despite of different purging methods. For this reason we decided to focus on allogeneic BMT. We have grafted five patients within the last 3 years. Three of them are alive and well, on died from veno-occlusive disease 70 days after BMT, and the remaining patient, grafted from a syngeneic donor, died from relapsing tumor. The main problem in neuroblastoma stage IV is resistance to chemotherapy. Intensification of the conditioning regimen or double autografting leads to a rate of toxic deaths close to 20% (Zucker, EBMT 1987) which is not tolerable. New improvements in the conditioning regimen have to be found to increase the effect of BMT.

Bone Marrow Transplantation↗
PubMed1989

Interferon-gamma upregulates the susceptibility of human neuroblastoma cells to interleukin-2-activated natural killer cells.

The influence of interferon-gamma on the susceptibility of neuroblastoma cells in cell-mediated killing was investigated. Neuroblastoma cells were only weakly susceptible targets for peripheral mononuclear cells. However, enrichment of natural killer (NK) cells or activation of NK cells with interleukin-2 resulted in a considerable increase of neuroblastoma cell lysis. Pretreatment of neuroblastoma targets with interferon-gamma additionally increased the susceptibility to enriched NK cells as well as to interleukin-2-activated NK cells. The conjugate formation between enriched NK cells and the neuroblastoma targets was not affected by the pretreatment of the targets with interferon-gamma. Concomitantly, treatment of the neuroblastoma targets with interferon-gamma resulted in a strong induction of otherwise poorly expressed major histocompatibility complex (MHC) class I antigen expression. These results suggest that the increased expression of MHC class I antigens on target cells is not always correlated with decreased sensitivity for NK cells but can also be followed by an increased susceptibility for NK cells.

Antigens, Neoplasm↗
PubMed1988

Cytotoxic effects of m-[131I]- and m-[125I]iodobenzylguanidine on the human neuroblastoma cell lines SK-N-SH and SK-N-LO.

As we have reported recently, the human neuroblastoma cell line SK-N-SH is able to take up and store m-iodobenzylguanidine (mIBG). This is in contrast to several other neuroblastoma cell lines, among which are SK-N-LO cells. Both cell lines were used in cell killing experiments with unlabeled and radioactive-labeled mIBG. Using 1-200 microCi m-[131I]IBG (1 h incubation time), only SK-N-SH cells could to a large extent be destroyed in a dose-dependent manner. This effect is completely caused by the radioactive labeling of the molecule, because unlabeled mIBG proved not to be toxic in the concentration range used in experiments with radiolabeled mIBG (30 nM-3 microM). The killing effect was strongly reduced when m-[131I]IBG with low specific activity (0.2-0.3 mCi/mg) was used instead of 20-30 mCi/mg. Similar effects in both cell lines were obtained using m-[131I]-and m-[125I]IBG. SK-N-SH cells that survived a first treatment with m-[131I]IBG were less sensitive to a second treatment. SK-N-LO cells were more sensitive against m-[131I]- and m-[125I]IBG than SK-N-SH cells if both cell lines are exposed to these radioactive compounds over a long period of time (24 h). The reason that only SK-N-SH cells could be destroyed in short-term incubation experiments is that mIBG is stored for approximately 7 days in these cells only. SK-N-LO cells could only be destroyed to a significant degree if m-[131I]IBG was permanently present in the test system. Bone marrow stem cells (CFU-c) also proved to be sensitive against m-[131I]IBG, although the effects were less pronounced than on SK-N-SH cells.

3-Iodobenzylguanidine↗
PubMed1987

Treatment of neuroblastoma with metaiodobenzylguanidine: results and side effects.

Between April 1984 and December 1985 we treated ten children suffering from neuroblastoma in a total of 25 metaiodobenzylguanidine (MIBG) courses. Five had had a relapse of neuroblastoma stage III or IV, three had never achieved a remission in spite of intensive chemotherapy, and two were treated with an unstable remission. The children were each administered from 1 to 5 courses with a dosage per course of between 1,295 and 9,065 MBq. The sum of the single doses during the whole course of therapy ranged between 3,145 and 21,904 MBq per child. Five of five children suffering from bone pain and fever became free of complaints during the first three treatment days. Six of eight children with manifest tumor at onset of therapy responded well to the treatment: response extended from transitory decrease in elevated catecholamine levels in serum and urine to complete disappearance of large abdominal tumor masses. We also observed a decrease in bone marrow involvement and a stabilization of osteolytic lesions. Seven of these eight children died in spite of a good response from 55 to 350 days after the first MIBG treatment course. The only side effect we witnessed was a reversible bone marrow depression. In three children we combined the MIBG therapy with bone marrow transplantation.

3-Iodobenzylguanidine↗