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R Bredehorst

Publications and source records attributed to R Bredehorst.

67 records · Page 4Linked to original sources
PubMed1978

ADP-ribosylated histone H1 from HeLa cultures. Fundamental differences to (ADP-ribose)n-histone H1 conjugates formed into vitro.

ADP-ribosylated histone H1 was isolated from intact HeLa cells grown for 24 h with[3H]-adenosine and compared with ADP-ribosylated histone H1 synthesized from [3H]NAD by isolated HeLa nuclei. Most (ADP-ribose)n-histone H1 conjugates formed in vivo carried single ADP-ribose units, less than one fourth of the total ADP-ribose residues being in the form of oligomeric or polymeric chains. (ADP-ribose)n linked to H1 in vivo was not released by neutral NH2OH to a significant extent. Alkali treatment (pH 10.5) liberated most but not all of the ADP-ribose residues which may indicate the existence of a new type of linkage so far found only in conjugates isolated from intact tissue. No ADP-ribosylated histone H1 complex of higher molecular weight ('H1 dimer') could be detected in intact cells. By contrast, isolated HeLa nuclei formed ADP-ribosylated histone H1 which contained predominantly polymeric ADP-ribose residues. The (ADP-ribose)n residues were linked by NH2OH-sensitive and by NH2OH-resistant, alkali (pH 10.5) labile bonds, the majority of the conjugates appearing in the form of the higher-molecular-weight complex. A comparison with the ADP-ribosylated non-histone proteins indicated that histone H1 formed in vivo carried less than 2.5% of the total protein-bound ADP-ribose residues and less than 1% of the protein-bound ADP-ribose synthesized in vitro.

Cell Nucleus↗
PubMed1978

Determination of ADP-ribose and poly(ADP-ribose) by a new radioimmunoassay.

A specific and sensitive radioimmunoassay for ADP-ribose has been developed on the basis of the selective conversion of ADP-ribose to 5'-AMP by alkaline treatment. Antibodies highly specific against 5'-AMP allowed quantification of ADP-ribose converted to 5'-AMP in the range of 1-40 pmol, and in the presence of large quantities of nucleic acids or 3'-AMP. Poly(ADP-ribose) could also be determined when degraded to ADP-ribose by poly(ADP-ribose) glycohydrolase. Determination of the chain length of purified polymer was possible by a parallel determination of ADP-ribose residues after glycohydrolase treatment and of 5'-AMP from the non-reducing end obtained by phosphodiesterase catalyzed hydrolysis. The high specificities of the alkaline conversion of ADP-ribose to 5'-AMP and of the radioimmunoassay for 5'-AMP allowed quantification of protein-bound ADP-ribose residues in crude tissue extracts as verified by comparison with chromatographically purified samples.

Adenosine Diphosphate Sugars↗
PubMed1976

Quantitative determination of poly(adenosine diphosphate ribose) in different hepatic tissues by an isotope dilution procedure.

A procedure has been developed for the quantitation of poly(ADP-ribose) in intact tissues. It is based on the dilution of added [3H]poly(ADP-ribose) by the endogenous polymer. 5 - 6 nanomoles protein-bound ADP-ribose per mg DNA were found in adult and neonatal rat liver, while Zajdela hepatoma cells had significantly lower values. A comparison with mono(ADP-ribose) residues in adult rat liver revealed similar levels of monomeric and polymeric ADP-ribose residues. This means that far more proteins (or acceptor sites on proteins) must be occupied by single ADP-ribose residues than by oligo or poly(ADP-ribose) chains. While the poly(ADP-ribose) levels of the different tissues do not correlate with the corresponding proliferation rates, the amount of mono(ADP-ribose) does show a certain Correlation, being low in rapidly growing tissues.

Animals↗
PubMedDate not supplied

Cobra venom factor immunoconjugates: effects of carbohydrate-directed versus amino group-directed conjugation.

Human IgM monoclonal antibody 16-88, derived from patients immunized with autologous colon carcinoma cells, was derivatized with two different cross-linkers, S-(2-thiopyridyl)-L-cysteine hydrazide (TPCH), which is carbohydrate-directed, and N-succinimidyl-3-(2- pyridyldithio)propionate (SPDP), which is amino group-directed. Two antibody functions, antigen binding and complement activation, were assayed upon derivatization with TPCH and SPDP. TPCH allowed for extensive modification (up to 17 TPCH molecules per antibody) without impairment of antigen binding activity, while this function was significantly compromised upon derivatization with SPDP. Antibody molecules derivatized with 16 SPDP residues showed almost complete loss of their antigen binding function. The complement activating ability of antibody 16-88 was significantly decreased after derivatization with TPCH or SPDP. In the case of SPDP derivatization, this decrease of the complement activating ability is predominantly a consequence of the impaired binding function. Upon conjugation of cobra venom factor (CVF), a nontoxic 137-kDa glycoprotein which is capable of activating the alternative pathway of complement, the antigen binding activity of SPDP-derivatized antibody was further compromised, whereas that of TPCH-derivatized antibody remained unaffected even after attachment of three or four CVF molecules per antibody. In both conjugates CVF retained good functional activity. CVF was slightly more active when attached to SPDP-derivatized antibody, suggesting a better accessibility of amino group-coupled CVF for its interaction with other complement proteins. These results indicate that carbohydrate-directed conjugation compromises the antibody function of complement activation, but allows for the generation of immunoconjugates with unimpaired antigen binding capability.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

[Natural human IgM-antibodies in neuroblastoma therapy: preliminary findings of a phase I/II clinical trial].

BACKGROUND: Sera from healthy individuals contain natural IgM antibodies (anti-NB-Ab) cytotoxic to neuroblastoma (NB) cells. In contrast to healthy children the prevalence of anti-NB-Ab in sera of NB patients is low. Binding of anti-NB-Ab to the NB cell surface leads to activation of complement in vitro. In vivo the injection of the purified IgM fraction from a cytotoxic blood donor results in complete growth arrest of NB xenografts in nude rats. Preliminary results from a phase I/II study to evaluate the pharmacokinetics and side effects of a therapy with anti-NB-Ab are presented here. PATIENTS: Included in this study are patients with NB stage 4 according to INSS with relapse or non-responders to therapy according to the GPOH-NB-therapy protocol. The patients are negative for anti-NB-Ab and are older than one year. METHODS: The therapy is based on a complete exchange of the anti-NB-Ab negative patient serum against serum from an anti-NB-Ab positive ABO-compatible donor by means of plasmapheresis. RESULTS: Up to now, 14 cycles of plasmapheresis have been carried out in 6 NB patients. In 13 of 14 therapy cycles a significant increase in serum toxicity could be observed. Severe side effects have not been seen except a catheter associated thrombosis which was reversible under heparin treatment. After plasmapheresis, pain in the tumor site or regions of metastasis did occur regularly. In some cases temporary elevation of body temperature occurred. One patient had a reduced MIBG uptake after therapy. Tumor necrosis was observed in 2 patients. Three patients showed tumor progress. CONCLUSION: Immunotherapy of NB in children by serum exchange using anti-NB-Ab positive ABO-compatible donor serum is feasible without major side effects and leads to a significant increase of serum toxicity against NB cells.

Child↗
PubMedDate not supplied

Naturally occurring humoral cytotoxicity against neuroblastoma (NB) cells in healthy persons and NB patients.

A novel cytotoxic mechanism against neuroblastoma (NB) cells based on natural immunoglobulin M serum antibodies is described. The occurrence of these antibodies, which are able to induce complement-mediated cytolysis of NB cells, has been investigated in several age groups of healthy persons and in patients with NB. The cytotoxicity of serum samples has been measured in terms of propidium iodide DNA incorporation using a FACScan. The prevalence of anti-NB 1gM antibodies shows a strong age dependence characterized by a nearly complete lack in the first year of life and a steep rise up to 82% beginning with the second year of life. In the sera of 11 NB-bearing patients no cytotoxicity has been found, despite the fact that 8 of these patients were older than 1 year. These findings lead to the hypothesis that natural 1gM antibodies could play a role as an immunological control mechanism against NB.

Antibodies, Neoplasm↗