Search PubMed⌕ Search

Biomedical subjects

W Hiddemann

Publications and source records attributed to W Hiddemann.

At least 271 records · Page 15Linked to original sources
PubMed1995

Highly sensitive high-performance liquid chromatographic assay for 1-beta-D-arabinofuranosylcytosine-5'-stearyl phosphate (cytarabine-ocfosfate).

An ion-pair HPLC method for the determination of 1-beta-D-arabinofuranosylcytosine-5'-stearyl phosphate (cytarabine-ocfosfate I) was developed, using a phenyl-bonded column under reversed-phase conditions with a mobile phase of acetonitrile-buffered water (pH 6.8) (50:50) for isocratic elution. A reproducible sample clean-up was achieved by solid-phase extraction. In order to reach the low limit of detection of 2 ng/ml, an enrichment switching system was used. The present validation leads to a limit of quantification of 5 ng/ml with a coefficient of variation (C.V.) of 10%. The total time of measurement was shortened by a back-flush procedure to restore the conditions after each run. UV detection at 275 nm was applied. The recoveries for plasma samples ranged from 56.4 to 64.1%, regardless of drug concentrations. The intra-assay C.V. was about 4% (40 measurements at four different concentrations). The inter-assay recovery (ten measurements over ten days) at a plasma concentration of 50 ng/ml was 57% with a C.V. of 8.25%. Based on this HPLC method, the pharmacokinetics of I were measured during a clinical phase I/II study.

Antineoplastic Agents↗
PubMed1995

Low incidence of mbr bcl-2/JH fusion genes in Hodgkin's disease.

Lymph node biopsies from 140 cases of Hodgkin's disease (HD) and from 30 non-malignant lesions were screened for the presence of t(14;18) translocations involving the major breakpoint region (mbr) of the bcl-2 gene and the joining region (JH) of the immunoglobulin heavy chain gene, using a polymerase chain reaction (PCR) assay with subsequent nucleotide sequencing of amplified bcl-2/JH junctional regions. Expression of the bcl-2 protein within the Hodgkin and Reed-Sternberg (HRS) cells was investigated in 86 cases of HD by immunohistochemistry on cryostat or paraffin sections. Although bcl-2 expression could be found in a proportion of neoplastic cells in up to one-third of HD cases, the frequency of t(14;18) gene fusions detected by PCR was low. We identified such gene fusions in only 3 out of 140 (2 per cent) HD cases, one biopsy of which presented with four clonally distinct bcl-2/JH sequences. No t(14;18) was found in any of 30 reactive lymph node lesions. All fusion gene sequences were unique regarding the localization of the chromosome 14 and 18 breakpoints and the extranucleotide N-insertions. None of these gene fusions conformed to t(14;18) breakpoint sequences previously characterized in our laboratories. Our findings point to a mere coincidence in some cases of HD lesions and cells carrying a t(14;18) in the same biopsy and argue against a significant role of bcl-2 in the pathogenesis of HD.

Base Sequence↗
PubMed1995

The effect of stem-cell factor, interleukin-3 and erythropoietin on in vitro erythropoiesis in myelodysplastic syndromes.

An inherent defect of erythroid differentiation at the colony-forming unit blast (CFU-blast) compartment and (or) an impaired response of early erythroid progenitors (BFU-E) to growth stimulation are both considered to contribute to anemia in myelodysplastic syndromes (MDS). With the intention of improving survival and growth of early erythroid progenitors we investigated the effect of stem-cell factor (SCF) and interleukin-3 (IL-3) alone and in combination with erythropoietin, on the in vitro erythropoiesis of 13 patients with MDS and of three normal controls. SCF and IL-3 alone did not promote erythroid colony growth in MDS, while 3 cases responded to erythropoietin alone. In each of these, BFU-E colony growth could be increased by SCF, which was also found in all normal bone marrows. Altogether 6 cases showed a significant enhancement of BFU-E colony numbers by the combination of SCF and erythropoietin as compared to erythropoietin alone (P = 0.036). Out of the 6 responding cases, 5 belonged to the FAB-classified subgroups refractory anemia (RA) and refractory anemia with ringed sideroblasts (RA/RS) (5/5), while 1 patient was classified as having refractory anemia with excess of blasts (RAEB) (1/4). No patient with refractory anemia with excess of blasts in transformation (RAEB-T) (0/4) responded. In spite of these positive effects, the absolute number of BFU-E colonies remained reduced in all MDS cases when compared to normal controls. IL-3 proved ineffective in increasing the response to erythropoietin in MDS although it increased erythropoietin-induced BFU-E formation in normal controls significantly. We conclude that the striking synergistic effect of SCF and erythropoietin on erythroid colony formation seen with normal bone marrow is conserved in most cases with RA and RA/RS. In RAEB and RAEB-T the intrinsic defect of the erythroid differentiation pathway cannot be overcome by SCF.

Erythroid Precursor Cells↗
PubMed1995

Effects of hexadecylphosphocholine on membrane phospholipid metabolism in human tumour cells.

Hexadecylphosphocholine (HePC) is an analogue of the antiproliferative alkyllysophospholipids (ALP). As these lipid-like compounds interfere with membrane lipid metabolism at several sites, we studied the effects of HePC on uptake and metabolism of inositol and choline, two important phospholipid precursor molecules in two sensitive cell lines, Raji and KB, and in a resistant variant of KB cells, KBr. HePC substantially inhibited the membrane uptake of inositol and of choline in KB and Raji. Inositol uptake of KBr cells was constitutively low and was not further decreased by HePC. In all three cell lines, uptake inhibition of choline was less pronounced. Uptake inhibition showed characteristics of a non-specific effect, probably due to the physicochemical properties of HePC as a "lyso" structure. Decreased uptake of inositol did not affect phosphoinositide synthesis. Cellular phosphatidylcholine (PC) metabolism seemed to be affected through inhibition of choline incorporation and enhancement of PC degradation in the two sensitive cells. In KBr cells, these effects were not observed.

Antineoplastic Agents↗
PubMed1995

Non-Hodgkin's lymphomas--current status of therapy and future perspectives.

Non-Hodgkin's lymphomas (NHL) are a heterogeneous group of disorders which can either be classified according to their biology, represented by corresponding counterparts of normal lymphocyte development as in the Kiel classification, or according to their clinical course, used in the Working Formulation. The recently proposed Revised European-American Lymphoma (R.E.A.L.) classification may unify both aspects and facilitate the comparability of international studies. Besides histology, the extent of disease still comprises the major determinant of therapy. In high-grade lymphomas combination chemotherapy with cyclophosphamide, hydroxydaunorubin, vincristine and prednisone (CHOP) represents the treatment of first choice, and may be restricted to 3-4 cycles in patients with limited stages of the disease when followed by involved field radiotherapy. In more extended, bulky stage II to IV disease, treatment must be extended to six courses of CHOP and, potentially, additional irradiation. Even in advanced states of the disease, long-term remission and potential cure are achieved in 30-50% of cases. In low-grade lymphomas, most patients present with advanced stages III and IV for which chemotherapy can be applied with palliative intention only. Hence, a watch-and-wait approach still seems appropriate outside clinical investigations until the disease requires a therapeutic intervention. This consists preferentially of chemotherapy of moderate intensity such as cyclophosphamide, vincristine and prednisone (COP) or prednimustine and mitoxantrone (PmM). In responding patients, maintenance therapy with interferon-alpha is currently being explored and may result in prolongation of disease-free and, possibly also, overall survival. In both high- and low-grade lymphomas, intensification of therapy by myeloablative chemotherapy or combined chemoradiotherapy followed by autologous bone marrow transplantation (ABMT) or peripheral stem cell transplantation provides a promising and potentially curative prospective. In addition, new cytostatic agents such as the purine analogues--fludarabine, chlorodeoxyadenosine and deoxycoformycin--enlarge the therapeutic spectrum. More experimental approaches consist of the application of immunotoxins or radioisotypes, coupled to monoclonal antibodies directed against lymphoma-specific antigens. Overall, the substantial advances that have been achieved in the understanding of the biology and pathogenesis of malignant lymphomas, as well as the current achievements of therapy and the new promising perspectives, justify the hope that curative therapy can soon be offered to an increasing proportion of patients with NHL.

Humans↗
PubMed1995

[Pharmacokinetics of buprenorphine in subcutaneous administration].

UNLABELLED: In this study investigations were carried out on pharmacokinetics of buprenorphine after it had been applied subcutaneously. Up to now no pharmacokinetic data exist using this kind of application with relevant clinical doses. METHODS: With 6 patients, who had major general surgery under balanced anaesthesia, buprenorphine was given in a single subcutaneous injection of 5 micrograms/kg bodyweight for postoperative pain relief. Over a period of 48 hours the level of buprenorphine in blood plasma was measured. The analyses were done with a modified HPLC method with electrochemical detection which is able to achieve measurements as low as 40 pg/ml of plasma. The pharmacokinetic values were calculated with the "Topfit" pharmacokinetic computerised programme. RESULTS: Whereas the period of time (tmax) to reach peak plasma concentration (Cmax) after subcutaneous application is much longer than with other parenteral application forms, the plasma concentration levels tend to be similar after 20 minutes. The most important finding of this study is that the mean terminal half-life (t1/2c) of buprenorphine is 23 hours. However, the presently available data for other application forms in respect to terminal half-life did not produce the same results. This can be explained by the use of insufficiently sensitive analytical procedures and by too short periods of observation of 3 and 13 hours respectively, leading to values of t1/2c of 2 and 5 hours. CONCLUSIONS: These results indicate that the terminal half-life (t1/2c) of buprenorphine is much longer than had been supposed. It confirms clinical findings of sufficient pain relief by showing measurable uptake of buprenorphine after subcutaneous application.

Aged↗
PubMed1995

Rationale for high-dose chemotherapy and application of haematopoietic growth factors in acute myeloid leukaemia.

High-dose chemotherapy in acute myeloid leukaemia (AML) is more effective and not associated with a higher risk of lethal complications during the induction phase as compared with less intensive regimens. This seemingly paradoxical finding is explained by the more rapid reduction of the leukaemic cell mass and the faster restoration of normal haematopoesis. In the most recent study on double induction therapy by the German AML Cooperative Group involving 665 adult patients with AML the rate of complete remission was 66%-73%. Haematopoietic growth factors used as part of the anti-tumour regimen offer a number of advantages. These include acceleration of haematopoietic recovery and the potential to enhance the sensitivity of leukaemic blasts when given prior to and during cytostatic therapy. New perspectives to further enhance the intensity of antileukaemic therapy may emerge from the introduction of peripheral stem cell transplantation into the treatment strategy.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1995

Bcl-2 protein expression in breast cancer in relation to established prognostic factors and other clinicopathological variables.

BACKGROUND: Bel-2 inhibits most kinds of programmed cell death and provides a selective survival advantage to various cell types. Bcl-2 is physiologically expressed in ductal epithelia of the normal breast. The biological significance of Bcl-2 (over)expression for the development and progression of breast cancer has still to be evaluated. PATIENTS AND METHODS: A series of 133 primary breast cancers was investigated for expression of the Bcl-2 protein by immunohistochemistry of paraffin-embedded tissue sections. Results were correlated with other variables of established or presumed predictive value. RESULTS: A significant positive correlation was observed between Bcl-2 expression and positivity for estrogen and progesterone receptors (p < 0.001). High proliferative activity as assessed by Ki-67 staining correlated inversely with Bcl-2 expression (p < 0.001). Bcl-2 immunostaining was not related to positivity for c-erbB-1. It was negatively associated with overexpression of c-erbB-2 (p = 0.04), whereas a strong positive correlation was found with expression of c-erbB-3 (p = 0.01). There was a significant inverse correlation between histological grading and immunoreactivity for Bcl-2 (p < 0.001). N0 tumors tended to be Bcl-2 positive, but differences were not statistically significant. CONCLUSION: Bcl-2 was detected predominantly in differentiated tumors. Expression was associated with other favorable histopathological features and predictors of positive clinical outcome. Loss of Bcl-2 expression seems to be linked to loss of hormonal regulatability, increased dedifferentiation and deregulated proliferation.

Breast Neoplasms↗
PubMed1995

Purine analogs in the treatment of low-grade lymphomas and chronic lymphocytic leukemias.

The purine analogs fludarabine (FAMP), 2-chlorodeoxy-adenosine (2-CDA) and 2-deoxycoformycin (DCF) comprise a novel group of agents with high activity in low-grade lymphoid malignancies. Although all three agents share several mechanisms of action, such as the induction of apoptosis, and toxic effects, such as prolonged immunosuppression, their activity appears to be different in different disorders. While FAMP and possibly also 2-CDA are highly active in chronic lymphocytic leukemia and low-grade follicular lymphomas, 2-CDA and DCF are most effective in hairy cell leukemia. However, prospective comparative evaluations are in progress and their results may ultimately help to define the appropriate indications for and potential side effects of these highly promising new agents.

Antibiotics, Antineoplastic↗
PubMed1995

Reversal of multiple drug resistance in vitro by phosphorothioate oligonucleotides and ribozymes.

In the present study we investigated the effectiveness of 14, 15 and 18 nucleotide antisense phosphorothioate oligonucleotides (S-ODNs) directed to four different regions of the published mdr-1 gene sequence to reduce the level of mdr-1 gene product (p170, P-glycoprotein) and its function in the over-expressing cell lines Lo-VoDxR, S180DxR and KBChR8-5. The highest efficiency in reduction of multiple drug resistance was obtained at a concentration of 2 microM. In proliferation assays a growth reduction of 50% was observed after exposure of doxorubicin-resistant cells to S-ODN3. p170 protein expression of the resistant cell line LoVoDxR was reduced to the level of the sensitive cell line LoVo as shown by Western blot analysis. S-ODN3 reduced the ID50 of the two human cell lines up to 60% (LoVoDxR) and 21% (KBChR8-5), respectively, but showed no effect in the murine cell line S180DxR. In contrast, S-ODN1 was most effective in the murine system (67% reduction of the ID50), less effective in LoVoDxR (34%) and exhibited no effect in cell line KBChR8-5. Based on the results with the antisense oligonucleotides, a ribozyme directed against the mRNA target region of S-ODN3 was designed. This ribozyme was able to reduce the mdr-1 mRNA in total RNA preparations from cell line LoVoDxR up to 80% after an incubation time of 6 h in the presence of 10 mM MgCl2 at pH 7.5. A modified ribozyme was investigated in cell culture and reduced chemo-resistance of the resistant cell line LoVoDxR and ex vivo cultured blasts of acute myeloid leukemia patients up to 50%.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

Mobilization of CD34-positive tumour cells in a patient with testicular mixed germ cell tumour.

Tumour cells from a patient with recurrent testicular germ cell cancer and bone marrow infiltration were found to express CD33 and CD34 in the absence of other haemopoiesis-associated antigens. After myelosuppression and treatment with G-CSF for stem cell mobilization, CD34-positive tumour cells were detected in the peripheral blood in addition to normal haemopoietic progenitor cells. The tumour cells were decreased in the leukapheresis product. Retrospectively, the appearance of tumour cells in the peripheral blood after stem cell mobilization was the first indication of impending relapse.

Adult↗
PubMed1995

Failure of orally administered dipyridamole to enhance the antineoplastic activity of fluorouracil in combination with leucovorin in patients with advanced colorectal cancer: a prospective randomized trial.

PURPOSE: A randomized trial was performed to investigate the ability of the nucleoside transport inhibitor dipyridamole (DP) to enhance the antitumor activity of fluorouracil (5-FU)/leucovorin (folinic acid [FA]). PATIENTS AND METHODS: One hundred eighty-one untreated patients with advanced colorectal cancer were randomized to receive 5-FU 600 mg/m2 plus FA 300 mg/m2 on days 2 to 4 with or without DP 75 mg orally three times daily on days 1 to 5. Cycles were repeated every 3 weeks. Only patients with documented tumor progression before therapy were eligible. 5-FU pharmacokinetics using high-performance liquid chromatography (HPLC) were assessed in 11 nonrandomized patients receiving paired cycles with or without DP. RESULTS: One hundred seventy-four patients were assessable for toxicity and response. There was no significant difference in toxicity, except DP-related headache in 24% of patients. An objective response rate of 15% (one complete response [CR] and 13 partial responses [PRs]) for 5-FU/FA and 13% (two CRs and nine PRs) for 5-FU/FA/DP was observed. The dose-intensity of 5-FU delivered was significantly higher (1.09- to 1.16-fold) for the DP-containing arm. Pharmacokinetic parameters of 5-FU did not differ significantly, except for a prolonged half-life (t1/2) induced by DP. The median time to progression (P = .8) and the median survival time (11.6 months for 5-FU/FA v 9.3 months for 5-FU/FA/DP; P = .14, log-rank test) were not different between treatment arms. CONCLUSION: Orally administered DP did not improve the antineoplastic activity of 5-FU/FA in patients with advanced colorectal cancer when used at this dose and schedule. The observed increase in 5-FU dose-intensity for FU/FA/DP was not clinically relevant.

Administration, Oral↗
PubMed1995

Improvement of hammerhead ribozymes cleaving mdr-1 mRNA.

Overexpression of the mdr-1 gene is one of the mechanisms involved in therapy induced drug resistance. Gene-specific reduction of mdr-1 overexpression in human cancer using antisense technology may be an efficient tool for the reduction of multiple drug resistance (MDR). The application of catalyticly active RNA species--the so-called ribozymes--represents a possible improvement of this molecular strategy using oligonucleotides due to the catalytic potential of ribozymes. In the present paper we investigated the catalytic activity of ribozymes directed against three different cleavage sites on the mdr-1 mRNA. We designed ribozymes against cleavage sites at position 2408 (GUC, ribozyme III), 2429 (CUC, ribozyme I), and 2440 (GUC, ribozyme II). At all these cleavage sites we investigated ribozymes containing a 14 nucleotide complementary sequence to the target RNA (ribozymes I14-III14); at two sites (I and II) additional ribozymes with a 24 nucleotide hybridizing sequence have been tested. Catalytic activity was dependent on ribozyme to target ratio, pH, MgCl2 concentration, and incubation time. The highest cleavage activity was found with ribozyme II14, which cleaved 91% of an 292 nucleotides long in vitro transcript of the mdr-1 mRNA within 15 h in the presence of 10 mM MgCl2. Ribozymes I14 and II24 exhibited very similar but 6-fold reduced activity compared to ribozyme II14. Ribozyme III14 showed little and ribozyme I24 no cleavage activity.

Base Sequence↗
PubMed1995

Blast cell proliferative activity and sensitivity to GM-CSF in vitro are associated with early response to TAD-9 induction therapy in acute myeloid leukemia.

The current study was undertaken to determine the relevance of leukemic blast cell proliferative activity, cellular parameters of Ara-C metabolism and the in vitro sensitivity to GM-CSF in association with the clinical response to TAD-9 induction therapy in 66 patients with de novo acute myeloid leukemia (AML). Proliferative activity was assessed by 3H-thymidine (3H-TdR) incorporation and thymidine kinase (TK) activity, parameters of Ara-C metabolism comprised the activities of deoxycytidine kinase (DCK) and DNA polymerase alpha (poly alpha) as well as Ara-CTP concentrations and 3H-Ara-C uptake into DNA. GM-CSF sensitivity was determined by in vitro incubation of blasts for 48 h with or without GM-CSF (100 U/ml) followed by an additional 4 h concurrent exposure to GM-CSF and 3H-TdR (0.5 microCi/ml). The following results were obtained as expressed by median values and ranges: 3H-TdR incorporation: 1.07 pmol/10(5) cells (0.0-10.1), TK: 7.3 pmol/min/mg protein (1.3-56.0), DCK: 9.3 pmol/min/mg protein (0.77-47.1), poly alpha: 1.7 pmol/min/mg protein (0.00-28.9), Ara-CTP: 53.3 ng/10(7) cells (13.3-211.0), 3H-Ara-C uptake: 0.06 pmol/10(5) cells (0.0-0.57). 3H-Ara-C uptake was correlated with 3H-TdR incorporation (r = 0.74) and with the (S-phase dependent) activities of TK (r = 0.73) and poly alpha (r = 0.71, but not with DCK activity or intracellular Ara-CTP content. Blast cells of 37 from 55 analyzed patients were found to be sensitive to GM-CSF stimulation as defined by an increase in 3H-TdR incorporation > or = 1.5-fold over control values after the 48 h GM-CSF exposure. In vitro data were related with clinical response to TAD-9 induction therapy in 43 patients with newly diagnosed AML, taking the blast cell reduction at day 10 or 16 to < 5% or > or = 5% residual blasts as early parameter for adequate or inadequate response, respectively. While neither 3H-Ara-C uptake, nor intracellular Ara-CTP concentration, TK nor DCK activity were predictive for response, a high 3H-TdR incorporation and a high poly alpha activity were associated with adequate blast cell reduction. Median values of 3H-TdR incorporation were 2.26 pmol/10(5) cells for patients with adequate blast cell clearance and 0.80 pmol/10(5) cells for patients with inadequate blast cell clearance (P = 0.11), the respective values for poly alpha were 3.22 pmol/min/mg protein for responders and 1.1 pmol/min/mg protein for non-responders (P = 0.0085).(ABSTRACT TRUNCATED AT 400 WORDS)

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1995

Trisomy 4 in 'stem cell-like' leukemic cells of a patient with AML.

CD34 positive progenitor cells were analyzed in the bone marrow aspirate from a patient with newly diagnosed AML FAB M4. The patient had trisomy 4 as sole cytogenetic abnormality and a dominant population of CD34 negative leukemic blasts. Karyotyping of the FACS isolated, minor subpopulation of CD34+/CD38-, 'stem cell'-like cells (incidence 0.29%) revealed trisomy 4 in 11/13 metaphases. No metaphases were obtained in the CD34 negative subpopulation. The experiments point to the existence of leukemic stem cells in the CD34+/CD38- compartment in AML patients with trisomy 4.

ADP-ribosyl Cyclase↗