Biomedical subjects

D Krebs

Publications and source records attributed to D Krebs.

At least 73 records · Page 4Linked to original sources

PubMed1995

The basic subdomain of the c-Jun oncoprotein. A joint CD, Fourier-transform infrared and NMR study.

The structural properties of the basic subdomain of the basic zipper (bZIP) protein c-Jun were examined by joint means of 1H-NMR, CD and Fourier-transform infrared (FTIR) spectroscopies. The basic subdomain (residues 252-281 in c-Jun) is responsible for sequence-specific recognition of DNA. A modified basic subdomain bSD (residues 1-35) and its N-terminal part and C-terminal part fragments (NP, residues 1-19; and, CP, residues 16-35) were prepared by solid-phase synthesis and purified by HPLC. In aqueous solution, in the absence of DNA, bSD behaved mostly as an unstructured peptide characterized by only 5% alpha helix. However, upon mixing bSD and a specific DNA fragment, i.e. a CRE(cAMP-responsive element)-containing hexadecanucleotide, the alpha helix was stabilized to an extent of 20% at 20 degrees C or 35% at 2 degrees C. At the same time, no significant change could be detected in the DNA spectra. Addition of trifluoroethanol to an aqueous bSD sample resulted in an increase of the alpha-helix content so that about 60% of alpha helix was found at a ratio of 75% trifluoroethanol (20 degrees C). These effects were reflected in both CD and FTIR measurements. Changes shown by the CD spectra during the process suggested a mechanism dominated by a two-state helix/unordered transition. NMR data, namely alpha H chemical shifts, NOE cross-peaks and NH temperature coefficients provided indications for extended or nascent helix structures within four short stretches dispersed along the sequence for c-Jun bSD, contrasting with the unique and continuous stretch reported for Gcn4 (yeast general control protein 4) bSD in aqueous solution. Trifluoroethanol stabilized the alpha-helix structure mainly at these four sites. The malleability of the basic subdomain of c-Jun was emphasized in relation to its ability to fit the DNA helix in adopting an alpha-helix structure. The complex formation apparently requires substantial conformational change from the peptide and only little from the oligonucleotide.

Amino Acid Sequence↗

PubMed1995

[Cryopreservation of human oocytes in the pronuclear stage with an automated "open system"].

In the period from June 1990 to February 1993, 718 excess pronucleated oocytes from 185 cycles were cryopreserved by using the "open freezing system" in our IVF-programme at the Department of Gynaecology and Hospital of the University of Bonn. 1.5 mol propanediol and 0.1 mol sucrose were used as a cryoprotectant. During this time 287, pronuclear oocytes were thawed; of these 245 survived the freezing process and were classified as intact. The survival rate in this study was 85.4%, though if only one intact pronuclear oocyte was transferred, no pregnancy could be achieved, whereas if two or three pronuclear oocytes were transferred, seven to ten pregnancies resulted, respectively (23.3% and 23.8% pregnancy rates). Eight healthy children have been born to date from four other ongoing pregnancies, one of them is a twin pregnancy.

Cell Survival↗

PubMed1995

[Immune reactions and survival of patients with ovarian carcinomas after administration of 131I-F(Ab)2 fragments of the OC 125 monoclonal antibody].

The activation of the idiotypic network seems to be a beneficial approach to the immunological therapy of ovarian cancer. In a retrospective study 62 patients with ovarian carcinoma (of which 57 could be evaluated) received 1 mg of 131J-F(Ab)2 OC 125 MAb one to five times after radical surgery and polychemotherapy. In twenty-eight patients (49%) a remarkable anti-idiotypic antibody (Ab2) response arose. The anti-idiotypic antibody (Ab2) plasma levels increased with increasing number of F(Ab)2 OC 125 MAb applications. The twenty patients (35%) who developed Ab2-concentrations > 10,000 U/ml had a significantly higher survival rate than the patients who showed weak (Ab2-concentrations < 10,000 U/ml) or no immunological response to 131J-F(Ab)2 OC 125 MAb treatment (p < 0.05).

Antibodies, Monoclonal↗

PubMed1995

[Value of the Clearplan Ovulation Test in sterility treatment].

Detection of ovulation is an essential step in sterility treatment. Determination of the luteinising hormone is the most reliable method, which is generally performed by serum analysis. In this study, we proved the reliability of LH analysis in urine. 44 cycles of 35 volunteers with regular ovulatory cycles were examined. From day 11 on, daily LH measurements were performed on serum and urine. Ovulation was established by ultrasound monitoring of follicular development and/or by progesterone detection in the luteal phase. The sensitivity was 89% for serum analysis and 97.5% for urine analysis. The specificity was 100% for both methods. Hence, LH detection in urine is a reliable and secure method for ovulation determination. As an advantage over serum analysis, it requires less consultations, thereby offering a less expensive and stress reduced treatment.

Adult↗

PubMed1995

Antiidiotypic antibodies in ovarian cancer patients treated with the monoclonal antibody B72.3.

Immunotherapy with monoclonal antibodies has become a hopeful approach to the adjuvant therapy of cancer patients. Recently, formation of antiidiotypic antibodies (Ab2) has been demonstrated in ovarian cancer patients after immunization with F(ab')2 fragments of the monoclonal antibody OC 125 (MAb OC 125). Preliminary results suggested that patients with high Ab2 serum concentrations had better survival rates compared to those where low or no Ab2 serum levels were detected. Beginning in 1992, 23 patients with advanced ovarian adenocarcinomas have been treated with repeated intravenous applications of the MAb B72.3, which is directed against the ovarian carcinoma associated antigen TAG-72. Five of them had been pretreated with several F(ab')2 MAb OC 125 infusions. Blood sample analysis revealed a remarkable antiidiotypic antibody (Ab2) response in 14 patients, with five patients developing high serum levels > 1000 U/ml. Ab2 serum concentrations increased with increasing number of Mab B72.3 applications. In terms of serum levels, corresponding antiidiotypic antibody responses in patients who received both the F(ab')2 MAb OC 125 and the MAb B72.3 differed considerably. We conclude that the use of MAb B72.3 may be an additional beneficial approach to the immunological therapy of ovarian cancer. Subsequent MAb B72.3 application after failure of the F(ab')2 MAb OC 125 may induce appreciable Ab2 serum concentrations and vice versa.

Animals↗

PubMed1995

In vitro activity of titanocenedichloride versus cisplatin in four ovarian carcinoma cell lines evaluated by a microtiter plate ATP bioluminescence assay.

Titanocenedichloride (MKT 4) is a novel anticancer drug with a broad spectrum of activity in mammalian tumors. We investigated the anticancer efficacy of MKT 4 versus cisplatin and its chemomodulation by buthionine sulfoximine (BSO) in four different human ovarian carcinoma (OvCA) cell lines derived from both primary (A2780. OTN 14) and recurrent tumors (SKOV-3 and OV-MZ-1b) using an in vitro microplate ATP bioluminescence assay (ATP-TCA). Sensitivity against cisplatin was higher in A2780 and OTN 14 compared with MKT 4, whereas the opposite was found in SKOV-3 and OV-MZ-1b cells. In A2780, SKOV-3 and OV-MZ-1b, the cytotoxicity of both agents could be effectively improved by BSO with supraadditive effects observed for MKT 4 in all three cell lines. In OTN 14, however, BSO treatment failed to increase the cytotoxicity of both cisplatin and MKT 4. These results suggest antineoplastic activity of MKT 4 in cisplatin-sensitive and mainly in cisplatin-resistant OvCA cells which can be significantly modulated by BSO-mediated glutathione depletion. Since antineoplastic activity of both cisplatin and MKT-4 observed in OTN 14 could not be reversed by BSO, other mechanisms of drug resistance different from the glutathione redox cycle are likely to be important for both metal compounds.

Adenocarcinoma↗

PubMed1995

[Detection of genetic alterations in sporadic breast tumors].

OBJECTIVE: Loss of heterozygosity (LOH) indicates the existence of tumor suppressor genes (TSG) in the affected chromosomal loci. In order to uncover the involvement of such genes, we analyzed LOH in different chromosomal regions of sporadic breast carcinomas. MATERIAL AND METHOD: 47 breast cancer patients were screened for LOH with microsatellite markers on 18 different loci. DNA fragments were amplified by PCR from tumor and reference tissue. The PCR products were run on 8% denaturing polyacrylamide gels and visualized by silver straining. RESULTS: The following LOH-rates were found for the different loci: D6S497 (6p21, WAF-Region): 0%, D7S495: 9%, D7S522: 13%, D7S523: 22%, D11S488 (11q24-25): 38%, D13s321 and D13s765 (13q13-14, Rb-Region): 30% and 17%, D13S260 and D13S267 (13q12.3, BRCA2-Region): 28% both, D16S539 (16q22-24, E-Cadherin-Region): 35%, D17S5 (17p13.3): 17%, TP53 (17p13.1): 32% D17S250 (17q11-12): 22%, D17S855 (17q21 within the BRCA1 gene): 25%, D17S579 (17q21 telomer from BRCA1): 13%, D17S846 (centromere from BRCA1): 17%, 17q24 (SSTR 2): 9%, D22S684 (22q12, NF2-Region): 20%. Overall 66% of the tumors exhibited LOH. Lymphnode positive tumors showed significantly higher LOH rates than lymphnode negative tumors. CONCLUSIONS: Highest LOH-rates were found on chromosomes 11, 13, 16 and 17 indicative of relevant TSG's in the examined loci. In addition the findings indicate prognostic relevance of multiple LOH's in breast cancer.

Alleles↗

PubMed1995

[Generation and activation of tumor-infiltrating lymphocytes (TIL) within the scope of lymphokine activated killer cell therapy (LAK-TIL therapy) in patients with advanced breast and ovarian carcinoma].

In this study we examined a combined immunotherapy using lymphokine activated tumor infiltrating lymphocytes and active specific immunotherapy with virus-modified tumor cells in disseminated breast and ovarian cancer patients. During the therapy a significant increase in cytotoxicity could be observed, which nevertheless could not be maintained after the end of therapy. In an ongoing prospective randomized study we are using antigen specific stimulated cytotoxic T-lymphocytes to extend this effect.

Adult↗

PubMed1995

[Evaluation of the value of triple diagnosis in prenatal medicine].

The evaluation for every new method of early diagnostics is the criterion of quality of previous methods. The Triple diagnostics in the prenatal medicine however does not fulfill the criterion of standard for example for early diagnostics in gynecological oncology. Particularly, the precision in laboratories cannot be safely assumed so that false positive as well as false negative results are possible. The consequences of this method of early diagnostics are uncertainty for patients and physicians and of high expenditure for both.

Amniocentesis↗

PubMed1994

False changes in CA 125 levels in ovarian cancer patients after infusion of OC125 fragments for diagnostic and therapeutic purpose.

The influence of human anti-OC125 antibodies formed after multiple infusions of OC125 F(ab')2 fragments on the apparent levels of CA 125 measured with four different tests were examined in two ovarian cancer patients. With the homologous Assay 1, involving only OC125 antibodies, false increases of CA 125 values were observed after infusion of OC125 fragments, which completely covered real CA 125. In contrast, with Assay 2, 3 and 4, which involve no OC125 antibodies as capture antibodies, only slight false increases occurred in the presence of very high anti-OC125 antibody concentrations. Interference was eliminated by addition of non-specific murine IgG in Assay 2 and 4, but not in Assay 1 and 3 indicating that the false increases in Assay 1 and 3 were caused by anti-idiotypic anti-OC125 antibodies. In the presence of elevated real CA 125, with Assay 2 and to a considerably lesser degree with Assay 4, an inhibitory effect of anti-OC125 antibodies became evident leading to false decreases of CA 125 values. In Assay 4 reduction of assay response was eliminated by addition of nonspecific murine IgG. The results confirm that all available CA 125 tests are influenced by interference with human anti-OC125 antibodies. Thus, CA 125 levels in patients who have been treated with OC125 fragments should be interpreted with care.

Adenocarcinoma, Papillary↗

PubMed1994

Monoclonal antibodies and idiotypic network activation for ovarian carcinoma.

Antibodies can be processed by the B- and T-cell systems and may lead to a selective activation of the immune system. The network structure of the immune system implicates the possibility of a selective immunization by the activation of idiotypic cascades. In a retrospective analysis, patients with advanced ovarian carcinoma, who had received MAb, against the cancer-associated antigen CA125 for diagnostic purposes, were analyzed for the production of anti-idiotypic antibodies, survival rate, and immunological effects. Furthermore, we started a prospective and randomized study for ovarian cancer patients, using a different antigen, TAG72, for the induction of idiotypic cascades. Our first results on 58 patients with advanced ovarian carcinomas showed that the induction of anti-idiotypic-antibodies against OC125 mimicking the TAA Class III CA125 leads to a prolongation of the survival rate, and, in extended stages, to an induction of antitumoral immunity, and that the induction of idiotypic cascades is also possible for different antigens like TAG72. Summarizing the activation of idiotypic network cascades seems to be a very effective way of intervention in the immune system of patients with advanced stages of ovarian carcinoma. A prospective study of the adjuvant approach seems to be necessary.

Antibodies, Anti-Idiotypic↗

PubMed1994

Idiotypic cascades after injection of the monoclonal antibody OC125. A study in a mouse model.

In an animal model, we evaluated the possibility to induce antibodies directed against the tumor-associated antigen CA125 by immunization with the anti-CA125 antibody OC125 via activation of the idiotypic network. Our results show that Balb/c mice, immunized by repeated administrations of F(ab')2-fragments of the OC125 antibody (Ab1), produced anti-idiotypic antibodies (Ab2). The binding of these antibodies to the OC125 could be completely inhibited by the antigen CA125, suggesting that the anti-idiotypic antibodies imitate the original target antigen of the OC125. After induction of these paratope-binding anti-idiotypic antibodies (Ab2 beta), a murine IgG-anti-CA125 (Ab3) response arose in the same mice. The induction of idiotypic cascades offers the possibility of immunization against tumor-associated antigens without using the original antigen and breaking antitumor tolerance.

Animals↗

PubMed1994

[400 cycles with assisted fertilization in severe teratozoospermia].

From May 1991 to July 1993, assisted fertilisation by micromanipulation (PZD, SUZI and ICSI) was performed in 397 cycles with severe teratozoospermia. In the second series of 152 cycles with SUZI, the pregnancy rate per cycle was 5% (10% per transfer). In the third series, the method was changed from SUZI to ICSI.

Embryo Transfer↗

PubMed1994

[GnRH agonist treatment for in vitro fertilization in hyperandrogenemia].

Luteinising hormone (LH) is essential for steroidogenesis and folliculogenesis. In hyperandrogenic patients, however, an increased androgen production with the consecutive development of polycystic ovaries is caused by elevated LH levels. Suppression of androgens by the use of a GnRH agonist (a) may be a causal therapeutic approach. Therefore, we initiated a study comparing the combined GnRHa/HMG stimulation with HMG alone in hyperandrogenic patients undergoing in-vitro fertilisation (IVF). Altogether, 62 cycles were treated. Group 1 (n = 33) received a single depot injection of 3.6 mg goserelin on cycle day 22 followed by individualised HMG stimulation 14 days later. Group 2 (n = 29) started with the HMG stimulation on cycle day 3. In group 1, a pregnancy rate per transfer of 36.4% was achieved compared to only 20% in group 2. There was a strikingly lower abortion rate in group 1 that resulted in a significantly higher on going pregnancy rate. The results are in favour of the combined GnRHa/HMG stimulation as a first line therapy for hyperandrogenic IVF patients.

Adult↗

PubMed1994

[Ovarian stimulation with various FSH/LH concentrations in an in vitro fertilization program].

Various stimulation regimes have been tried to induce multiple follicular development for in-vitro fertilisation and embryo transfer. Human menopausal gonadotrophins have been widely used to induce follicular growth. To evaluate the role of the FSH: LH-ratio and the importance of LH concentrations, the results of a randomised assessor-blind group comparative efficacy and safety study are described. The effects of preparations, comprising FSH: LH-ratio of 3:1 and FSH: LH-ratio of 1:1 respectively, in stimulation of the ovaries for in-vitro fertilisation in infertile women are compared. Patients under 38 years of age with regular menstrual cycle (27 +/- 3 days and 32 +/- 3 days) are included. Sperm parameters have to be in normal range, according to WHO criteria. Follicular and luteal hormone parameters, ultrasound measurements, oocyte quality, fertilisation, cleavage and pregnancy rates are reported. The outcome of in-vitro fertilisation after the administration of preparations containing different ratios of FSH:LH leads to comparable results. However, the rate of ovarian hyperstimulation syndrome and the abortion rate after embryo transfer seems to be lower in patients stimulated with FSH dominant gonadotrophins.

Dose-Response Relationship, Drug↗

PubMed1994

[Suppression of endogenous LH increase in ovarian stimulation with the GnRH antagonist Cetrorelix].

Surges of LH in serum, which result in luteinization, but occur prematurely with respect to the diameter of the leading follicle, frustrate attemps to induce multiple follicular maturation for in-vitro fertilisation in a number of women. We examined the possibility of blocking premature LH-surges by the administration of Cetrorelix, a potent antagonist of gonadotrophin releasing hormone. Twenty patients, who had repeatedly shown premature LH surges, were treated with human menopausal gonadotrophins from the 2nd day onwards. From the 7th day until the induction of ovulation by HCG, the GNRH-antagonist Cetrorelix was given daily. HCG was injected when the dominant follicle had reached the diameter of at least 18 mm and oestradiol levels were above 300 pg for each follicle and more than 15 mm. Oocyte collection was performed 36 hours later by transvaginal ultrasound puncture, followed by IVF and embryo transfer. The hormone profiles of these patients and the results of in-vitro fertilisation and embryo transfer are discussed. It could be demonstrated in this study, that combined treatment with gonadotrophins and the GNRH-antagonist seems to be a promising method for ovarian stimulation in patients, who frequently exhibit premature LH discharges and therefore fail to complete treatment.

Adult↗

PubMed1994

Suppression of the endogenous luteinizing hormone surge by the gonadotrophin-releasing hormone antagonist Cetrorelix during ovarian stimulation.

Surges of luteinizing hormone (LH) that result in luteinization but occur prematurely with respect to the diameter of the leading follicle, prevent attempts to induce multiple follicular maturation for in-vitro fertilization (IVF) in a significant number of women. We examined the possibility of blocking premature LH surges by the administration of Cetrorelix, a potent antagonist of gonadotrophin-releasing hormone (GnRH), in a study including 20 patients, some of whom had previously shown premature LH surges. All patients were treated with human menopausal gonadotrophins (HMG) starting on day 2. From day 7 until the induction of ovulation by human chorionic gonadotrophin (HCG) the GnRH antagonist Cetrorelix was given daily. HCG was injected when the dominant follicle had reached a diameter of > or = 18 mm and oestradiol concentration was > 300 pg/ml for each follicle having a diameter of > 15 mm. Oocyte collection was performed 36 h later by transvaginal ultrasound puncture, followed by IVF and embryo transfer. The hormone profiles of these patients and the results of IVF and embryo transfer are comparable to those treated with GnRH agonists and HMG. However, less time and especially less HMG is needed in comparison to patients stimulated with a long agonist protocol. Hence, treatment with Cetrorelix proved to be much more comfortable for the patient. In this study we showed that combined treatment with gonadotrophins and the GnRH antagonist Cetrorelix is a promising method for ovarian stimulation in patients who frequently exhibit premature LH surges and therefore fail to complete treatment.

Adult↗

PubMed1994

Specific interference with the determination of the tumour-associated glycoprotein 72 by human anti-idiotypic antibodies formed after treatment with the anti-tumour-associated glycoprotein 72 antibody B72.3.

Recorded concentrations of the tumour-associated glycoprotein 72 (TAG-72) in ovarian cancer patients after repeated infusion of the antibody B72.3 were found to be falsely elevated when measured with an homologous immunometric assay involving the anti-TAG-72 antibody B72.3 (Test 1), or with an heterologous assay involving CC49 capture and B72.3 detector antibodies (Test 2). Test 1 yielded falsely elevated values up to 10(4) kU/l. Test 2 gave slightly false positive elevations up to 10(2) kU/l for only some of the samples with very high false-positive values in Test 1. The interfering serum components bound to Protein G-Sepharose and could be precipitated with perchloric acid or by heating serum samples to 100 degrees C. Addition of non-specific murine immunoglobulins only partly suppressed false-positive values in both tests. Our results suggest that this interference is caused by human anti-B72.3 IgG induced by B72.3 application, which to some extent specifically binds to determinants of the B72.3 antibody. Heat extraction of serum samples effectively eliminated interferences probably caused by anti-idiotypic antibodies, but did not affect real TAG-72.

Animals↗