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Biomedical subjects

M Löffler

Publications and source records attributed to M Löffler.

At least 19 recordsLinked to original sources
PubMed1992

[Recurrence of Hodgkin's disease after advanced primary stages. German Hodgkin's Study Group].

In a multicentre study on the treatment of Hodgkin's disease, 88 out of 297 patients with primary advanced stages IIIB/IV failed to respond to alternating COPP/ABVD chemotherapy +/- radiotherapy. They may be broken down as follows: tumour progression under current therapy (PD) 23/28, partial remission at the end of treatment (PR) 28/88, early nodal recurrence 13/88, late nodal recurrence 15/88, extranodal recurrence 7/88, unclear localisation 1/88. Thirty-six months after noting failure of treatment, 45% of all patients were still alive. The prognosis was poorest in the case of primary PD. Only 1/23 of these patients experience lasting complete remission thanks to salvage treatment (cCR). Eleven patients with an exclusively nodal recurrence experienced a cCR on treatment with radiation alone, and may be considered a low-risk recurrence group. For a high-risk recurrence group (n = 57), indication for high-dose chemotherapy with subsequent autologous bone marrow transplantation (HDC/ABMT) should have been recognized on the basis of the present definition. The survival probability of these patients, who only received conventional salvage treatment, was 38% after 30 months (95% confidence limit, 22 to 54%). These data would not appear to be appreciably poorer than those reported in the literature for comparable patients receiving HDC/ABMT. Only a randomized comparison would be capable of showing whether HDC/ABMT is superior to high-dose conventional chemotherapy with haematopoietic growth factors. It is proposed that such a therapeutic trial should be initiated as soon as possible.

Adolescent↗
PubMed1992

The "anti-pyrimidine effect" of hypoxia and brequinar sodium (NSC 368390) is of consequence for tumor cell growth.

The rationale of the present study was to investigate the simultaneous effect of hypoxia and drugs with an "anti-pyrimidine effect" on tumor cell proliferation to evaluate putative changes in the sensitivity of cells to these kinds of chemotherapeutic treatment on reduced O2 tension. Pyrimidine de novo biosynthesis, at the stage of respiratory chain-dependent dihydroorotate dehydrogenase, was found to be a biochemical target site for oxygen deficiency as well as for Brequinar Sodium (6-fluoro-2-(2'-fluoro-1,1'-biphenyl-4-yl)-3-methyl-4-quinoline carboxylic acid sodium salt) (Brequinar). Increasing drug concentrations (0.1-50 microM) reduced the proliferation rate of in vitro cultured Ehrlich ascites tumor cells (IC50 = 0.25 microM). Decreasing concentrations of O2 reduced the proliferation rate (50% at approximately 3.5% O2). Brequinar at 2.5 microM stimulated the incorporation of exogenous [14C]uridine into RNA to 140 and 190% of controls, respectively, as a result of active salvage pathways, whereas it decreased the incorporation of [14C]NaHCO3 by the de novo pathway (to 20 and 5% of controls, respectively). Cells routinely grown in glucose-free, uridine-supplemented medium were resistant to 12.5 microM of the drug. The complete growth pattern of the tumor cells (increase in cell number and protein, RNA and DNA content of cultures during a 24-hr culture period) was examined (i) on reducing the O2 tension of the atmosphere stepwise from 20 to 1% O2; (ii) on addition of 0.125 microM Brequinar; and (iii) under both conditions. The combination was found to give an additive inhibitory effect under moderate hypoxia (5-20% O2) and a greater than additive effect if the oxygen tension was further reduced (1-5%).

Animals↗
PubMed1992

Differential susceptibility of dihydroorotate dehydrogenase/oxidase to Brequinar Sodium (NSC 368 390) in vitro.

To verify the assumption of a specific and potent drug action on de novo pyrimidine biosynthesis, isolated dihydroorotate dehydrogenase (DHO-DH) (EC 1.3.3.1) was exposed to Brequinar Sodium (6-fluoro-2-(2'-fluoro-1,1'-biphenyl-4-yl)-3-methyl-4-quinoline carboxylic acid sodium salt, NSC 368 390) (Brequinar). The membrane-bound DHO-DH was purified to apparent homogeneity (25,000-fold) from rat liver mitochondria in six steps via detergent extraction and subsequent chromatography using the dye ligand Matrex Gel Orange A. Using molecular mechanistic studies (MM2) this ligand was found to mimic closely the stereochemical conformation of Brequinar. SDS-PAGE revealed two protein bands for the purified enzyme with apparent molecular masses of 58 (major) and 68 kDa (minor). In vitro, two modes of action of the DHO-DH are possible: (i) acting as a dehydrogenase in the presence of ubiquinone as proximal electron acceptor and (ii) direct reaction with oxygen as oxidase. A novel assay for the measurement of the oxidase activity was adapted using leuco-dichlorofluorescein-diacetate. Inhibition experiments revealed a striking difference in the susceptibility of DHO-dehydrogenase/oxidase to Brequinar: apparent Ki = 6.09 +/- 0.05 (SD) nM (DHO; ubiquinone n = 10), but Ki = 3.10 +/- 0.09 (SD) mM (DHO; O2). Analyses of initial velocity experiments showed non-competitive inhibition of Brequinar with respect to the substrate dihydroorotic acid in both assays (dehydrogenase and oxidase). The inhibitory effect of the latter was compared to that of the competitive inhibitor 5-aza-dihydroorotate (apparent Ki = 15 +/- 0.25 (SD) microM). The present kinetic data on the action of the purified rodent DHO-DH with Brequinar and computer-aided analyses provide a better insight into the drug-enzyme interaction.

Animals↗
PubMed1992

HLö 7 dimethanesulfonate, a potent bispyridinium-dioxime against anticholinesterases.

HLö 7 dimethanesulfonate (1-[[[4-(aminocarbonyl)pyridinio]methoxy]methyl]-2,4-bis [(hydroxyimino)methyl]pyridinium dimethanesulfonate) is a broad-spectrum reactivator against highly toxic organophosphorus compounds. The compound was synthesized by a new route with the carcinogenic bis(chloromethyl)ether being substituted by the non-mutagenic bis(methylsulfonoxymethyl)ether. The very soluble dimethanesulfonate of obidoxime was also prepared by this way. HLö 7 dimethanesulfonate is the first water-soluble salt of HLö 7 that should be suitable for the wet/dry autoinjector technology, because aqueous solutions of HLö 7 are not very stable (calculated shelf-life 0.2 years when stored at 8 degrees C, 1 M solution, pH 2.5). The crystalline preparation contains 96% of the syn/syn-isomer, less than 2% of the syn/anti-isomer and some minor identified by-products. HLö 7 was very efficient in reactivating acetylcholinesterase (AChE) blocked by organophosphates as long as ageing did not prevent dephosphylation. HLö 7 was superior to HI 6 (1-[[[4-(aminocarbonyl)pyridinio]methoxy]methyl]-2- [(hydroxyimino)methyl]pyridinium dichloride) in reactivating soman and sarin-inhibited AChE from erythrocytes, and literature data indicate that HLö 7 exceeds HI 6 by far in reactivating tabun-inhibited AChE. In atropine-protected, soman-poisoned mice HLö 7 was three times more potent than HI 6 (protective ratio 5 versus 2.5), and in sarin-poisoned mice HLö 7 was 10 times more potent than HI 6 (protective ratio 8 for both oximes). In atropine-protected guinea-pigs HLö 7 was less effective than HI 6 (protective ratio: 2.3 versus 5.2 for soman; 5.2 versus 6.8 for sarin; 4.3 versus 3.8 for tabun). The mean survival time of anaesthetized guinea-pigs exposed to 5 LD50 soman (6.3 min) was increased by atropine (27 min) and atropine + HLö (57 min). HLö 7 alone did not prolong the survival. The most impressive effect of HLö 7 was on respiration: 3 min after i.v. injection of HLö 7 and atropine, the depressed respiration increased rapidly to 60% of control and remained at that level during the observation period (60 min). With atropine alone, respiration recovered only slowly. Behavioural and physiologic parameters were determined in atropine-protected mice exposed to a sublethal soman dose. The running performance was significantly improved by HLö 7. Even central symptoms, e.g. hypothermia and convulsions, were decreased markedly by HLö 7 (evaluation 60 min after poisoning). The pharmacokinetic data for HLö 7 in male beagle dogs are similar to those of HI 6.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

A cytokinetic approach to determine the range of O2-dependence of pyrimidine(deoxy)nucleotide biosynthesis relevant for cell proliferation.

In vitro cultured Ehrlich ascites tumour (EAT) cells were used because of the ease of their manipulation under different levels of hypoxia. They were used to clarify further the complex mechanism of oxygen-dependent cell proliferation. On reducing the oxygen concentration from 20% to lower levels (1-7%) an increase in the length of the population doubling time with concomitant reductions in protein, RNA and DNA content of cultures were observed. The incorporation of [14C]HCO3- into the RNA fraction of cells by de novo biosynthesis of uridine monophosphate (UMP) was reduced proportionally to the microenvironmental O2 tension. Uptake of this labelled precursor by cells in the presence of N-phosphonoacetyl-L-aspartate was found to be similarly inhibited. To correlate the reduction of cell growth under hypoxia with the functional pyrimidine supply, hypoxic cells were cultured in the presence of a balanced mixture of deoxynucleosides and/or uridine (100 microM deoxycytidine, 10 microM deoxyadenosine, 10 microM deoxyguanosine, 100 microM uridine). Above 3% O2 in the protective atmosphere, no improvement of growth parameters by the exogenous pyrimidinenucleotide precursors was obtained, whereas these compounds had a positive influence below this level. The increase in cell number was raised to about 60% of that of control cultures (20% O2) irrespective of the oxygen tension. In addition, when above 3% O2 the incorporation of HCO3- into RNA was comparable to that of controls, indicating that the pyrimidine de novo pathway is not a limiting factor in RNA biosynthesis. In conclusion, whereas at suboptimal O2 levels (5-7%) no correlation between pyrimidine metabolism and reduction of proliferation rate appears to exist, at low O2 concentrations (less than 3%) the rate of orotate/UMP production seems to be an important factor in the growth cessation of EAT cells; at critical O2 tensions (less than 1%) the lack of pyrimidine-deoxynucleosides substantially reduces cell cycle progression.

Animals↗
PubMed1992

The Second International Symposium on Hodgkin's Disease. Workshop III: Recommendations for future clinical trials.

In the opinion of the participants of the workshop, the following problems should be addressed with high priority: 1st, a clear definition of the 10%-15% of patients who should receive radiotherapy only; 2nd, reduction of toxicity of combined modality approaches for patients in localized stages with risk factors; and 3rd, definition of a poor-prognosis subgroup of patients in stages IIIB/IV for whom more efficient treatment programs must be developed. Dose intensification in the form of ABMT as the prominent example of high dose intensity should be tested in these patients. If this approach proves its efficacy, the concept of dose intensification could be extended to other patients with advanced disease. Results of recent trials in Hodgkin's disease suggest that the cure rates which increased considerably between 1960 and 1980 have reached a plateau. Further improvements that can be realistically expected will be small and studies to prove such progress need large numbers of patients ('megatrials') to avoid 'false negative' results. Such megatrials could be performed as large international or even intercontinental trials. To some extent, overviews could substitute for megatrials, if sufficient high-quality randomized studies addressing a specific question are available for a meta-analysis. The installation of an international steering committee was recommended, which should stimulate and coordinate world-wide efforts for the solution of the remaining problems in the treatment of Hodgkin's disease.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1990

Increased level of histone H1(0) messenger RNA in hypoxic Ehrlich ascites tumor cells.

We have investigated the expression of the H1 histone subtype H1(0) gene in Ehrlich ascites tumor cells (EAT) under varied conditions of oxygen supply. Our results show that proliferating EAT cells express H1(0) mRNA at a basal level under normoxic conditions. Severe hypoxia leads to a cessation of cell growth and causes an accumulation of cells in G1. Here, we show that the level of H1(0) histone mRNA increases within a few hours after the onset of hypoxia.

Animals↗
PubMed1990

[Radiotherapeutic quality assurance in the Hodgkin's disease study HD4 supported by the BMFT (Bundesministerium für Forschung und Technologie)].

In the German Hodgkin Study Group a radiotherapy assurance program is being carried out at the radiotherapeutic reference centre in Göttingen since April 1988: 74 patients were entered from 27 radiotherapeutic institutions. 18 of them participated in a quality assurance program and submitted the data of 29 patients: In 21 of the 29 patients the protocol was followed correctly. Physical aspects of quality control showed two major deviations from the protocol: one center used photon energies of more than 15 MVX without mould; another had a anterior-posterior loading of 3:1. The radiation oncology assessment detected six inadequate treatments: The safety margin was inappropriate in three of 26 mantle fields. Another center used a multiple field technique, and in two patients the paraaortic region was not irradiated.

Cobalt Radioisotopes↗
PubMed1990

[Aspects of family-oriented diagnosis in compulsory legal family expert assessment].

In forensic psychology, recommendations that courts request when granting one of the parents the right of child upbringing after a divorce pose a problem for the person who is required to give such expert judgment. The authors describe the difficult situation he faces when having to decide for and, at the same time, against one of the parents. A good knowledge of family psychology and pathopsychology is essential, and for drawing up the expertise and stating his reasons, the expert requires methodical resources. The authors describe four procedures of relational diagnosis and recommend the combined use of these in conjunction with methods that have been employed so far.

Child↗
PubMed1989

The bispyridinium-dioxime HLö-7. A potent reactivator for acetylcholinesterase inhibited by the stereoisomers of tabun and soman.

Purification of (+)-tabun was accomplished by treatment with electric eel acetylcholinesterase (AChE) in order to bind contaminating (-)-tabun and with purified (+)-tabun shown similar properties in reactivation reactions with oximes (pH 7.5, 25 degrees). The bispyridinium-2,4-dioxime HLö-7 is a substantially active reactivator for these inhibited enzymes as well as for human erythrocyte AChE inhibited with (-)-tabun. In contrast, the corresponding bispyridinium-2-monooxime HI-6 does not show any activity at similar reaction conditions. HLö-7 is also much more active than HI-6 when used as a reactivator for electric eel AChE inhibited by some N-unsubstituted derivatives of tabun. Surprisingly, HLö-7 is highly active in reactivating human erythrocyte and rat diaphragm AChE inhibited by C(+)P(+/-)-and C(-)P(+/-)-soman, i.e. at least as active as HI-6, which is the most potent reactivator for soman-inhibited AChE reported so far. To our knowledge, HLö-7 is the first compound reported in literature that shows a potent reactivating activity towards both tabun-inhibited AChE and soman-inhibited AChE.

Acetylcholinesterase↗
PubMed1989

Simultaneous analysis of mitochondrial activity and DNA content in Ehrlich ascites tumor cells by dual parameter flow cytometry.

Ehrlich ascites tumor cells were permeabilized using low concentrations of digitonin, 8 micrograms/10(6) cells. Permeabilization was monitored by the assay of lactate dehydrogenase released into the incubation medium and of hexokinase partially bound to mitochondria. Integrity of the cellular organelles was unaffected as determined by assay of the mitochondrial enzyme glutamate dehydrogenase. Cells were stained with rhodamine 123 as a mitochondrial specific dye and propidium iodide/mithramycin as DNA specific dyes. The green fluorescence of bound rhodamine 123 versus red fluorescence of DNA in individual cells was analysed by dual parameter flow cytometry. Incubation of cells with inhibitors of mitochondrial energy metabolism, such as, potassium cyanide and carbonyl cyanide m-chlorophenylhydrazone abolished binding of rhodamine 123. Flow cytometric data allowed a correlation between cell position in the mitotic cycle with total mitochondrial activity. In addition, comparison of the characteristics of propidium iodide and ethidium bromide staining further elucidated the molecular basis of the staining with the positively-charged fluorescent dye rhodamine 123.

Animals↗
PubMed1989

Chemotherapy of Hodgkin's lymphoma with alternating cycles of COPP (cyclophosphamide, vincristin, procarbazine, prednisone) and ABVD (doxorubicin, bleomycin, vinblastine and dacarbazine). Results of the HD1 and HD3 trials of the German Hodgkin Study Group.

Untreated patients with Hodgkin's lymphoma in stages I-IIIA with risk factors (large mediastinal mass, massive splenic involvement, extranodal disease) were entered into the HD1 protocol and received a combined chemo-radiotherapy [2 X (COPP + ABVD) + 40 Gy extended field irradiation (EF) vs 2 X (COPP + ABVD) + 20 Gy EF]. Patients in stages IIIB/IV (HD3 protocol) received induction chemotherapy [3 X (COPP + ABVD)] and were randomized into consolidation by radiotherapy [20 Gy involved field irradiation (IF)] vs chemotherapy [1 X (COPP + ABVD)]. Seventy-three of 89 evaluable patients (82%) treated according to the HD1 protocol achieved a complete remission. Freedom from progression and survival of patients in stages I-IIIA with risk factors treated according to HD1 were no worse than those of patients in stages I and II without risk factors who received only radiotherapy. Eighty-six of 137 patients (63%) treated according to the HD3 protocol achieved complete remission after induction chemotherapy with COPP + ABVD. This is significantly better than the 31% complete remission rate observed in a previous pilot study with COPP alone (P less than 0.01). Including salvage therapy (radiotherapy in case of persisting nodal disease; chemotherapy with 4 X CEVD in case of persisting disseminated disease), a total of 76% complete remissions in stages IIIB/IVAB were achieved. A high erythrocyte sedimentation rate (greater than 80 mm h-1) was the most significant risk factor for achieving freedom from progression.

Adolescent↗
PubMed1989

The biosynthetic pathway of pyrimidine (deoxy)nucleotides: a sensor of oxygen tension necessary for maintaining cell proliferation?

Culture experiments on Ehrlich ascites tumor cells revealed that a low oxygen tension (about 20% in normoxic atmosphere) induced an increase in the length of the growth cycle. The relative growth of aerobic control cells after transfer to the second in vitro passage was 145% within 24 h, and reduced to 50% at 1% O2 and about 30% at 0.1% O2. The increase in protein and DNA content of these hypoxic cultures was equally impaired. Also, the cell cycle traverse as analyzed by flow cytometry was affected predominantly at the G1/early S stage. Uptake of labeled thymidine into acid-insoluble material of hypoxic cells was below that of controls whereas incorporation of uridine exceeded that of normoxic controls. Supplementation of cells cultured under 0.1 and 1% O2 with 0.1 mM uridine or 0.1 mM deoxycytidine + 0.01 mM deoxyadenosine and deoxyguanosine improved all growth parameters; deoxynucleosides were more effective than uridine in cells under 0.1% O2 whereas in cells cultured under 1% O2 similar effects of both were observed. This points to an insufficient supply of nucleic acid precursors even under moderate limitations of oxygen tension and not only under strict hypoxia. Whereas a 12-h cultivation time at 0.1% O2 hardly impaired cell growth after reoxygenation, a cultivation time of 24 h considerably reduced the cellular capability to recover. This was alleviated by addition of (deoxy)nucleosides from the beginning of hypoxic culture. The results are interpreted as supporting the concept that the biosynthetic pathway of pyrimidine (deoxy)nucleotides--because of two oxygen-dependent enzymes, dihydroorotate dehydrogenase and ribonucleotide reductase--is a potential transducer of environmental limitations in oxygen tension to the proliferative capacity of cells.

Animals↗
PubMed1988

[Therapy of Hodgkin's lymphomas. Results of the German Hodgkin's Disease Study Group].

Between July 1983 and May 1987 143 untreated patients with Hodgkin's lymphoma in stages I-IIIA with risk factors qualified for the HD1 protocol, and 230 patients in stages IIIB/IV qualified for HD3. Patients in HD1 received a combined chemo-radiotherapy (2 x COPP + ABVD + 20 Gy EF vs. 40 Gy EF). Patients in HD3 received induction chemotherapy (3 x COPP + ABVD) and were randomized into consolidation by radiotherapy (20 Gy IF) vs. chemotherapy (1 x COPP + ABVD). In HD1, 73 of 89 evaluable patients (82%) achieved a complete remission. The survival of patients in stages I-IIIA with risk factors treated according to HD1 is as good as the survival of patients in stages I and II without risk factors. In HD3, 86 of 137 patients (63%) achieved complete remission after induction chemotherapy with 3 x COPP + ABVD. This is significantly better than the 31% complete remission rate observed in a pilot study with COPP alone (p less than 0.01). Including salvage therapy (radiotherapy in case of persisting nodal disease; chemotherapy with 4 x CEVD in case of persisting disseminated disease), a total of 76% complete remissions in stages IIIB/IVAB were achieved. An ESR greater than 80 mm/h was the most significant single risk factor in stages IIIB/IV for induction of CR and freedom from progression.

Adolescent↗
PubMed1987

Restimulation of cell cycle progression by hypoxic tumour cells with deoxynucleosides requires ppm oxygen tension.

Continuous exposure of Ehrlich ascites tumour cells to argon-CO2 under in vitro conditions caused rapid cessation of cell proliferation. On fixing the O2 level at 10 ppm in the protective atmosphere (0.001% in comparison with about 20% in normoxic atmosphere), G1 and early S cells remained stationary while G2 cells continued to pass from G2 into mitosis, to remain in a non-growing state in G1 of the subsequent cycle. Re-aeration of cells following 12 h hypoxia induced up to 25% of the population to continue DNA synthesis without a preceding cell division, as revealed by flow-cytometric analysis. Supplementation of cells cultured under hypoxia with a combination of deoxynucleosides (100 microM deoxycytidine, 10 microM deoxyadenosine, 10 microM deoxyguanosine) was found to stimulate reprogression through the cycle, provided the residual oxygen tension in the protective atmosphere exceeded 40 ppm. The increase in the number of cells with a DNA content of more than 4 C and in the number of binucleate cells observed after re-aeration of hypoxic cells was not prevented by deoxynucleosides or by uridine, which were present in the medium either during hypoxia of from the beginning of reoxygenation. These results indicate that the development of polyploidy as a result of oxygen deficiency cannot be influenced by improvement of RNA and DNA synthetic precursors.

Anaerobiosis↗