Biomedical subjects

P Pfeiffer

Publications and source records attributed to P Pfeiffer.

At least 73 records · Page 4Linked to original sources

PubMed1995

[Meningeal carcinomatosis in solid tumors].

Meningeal carcinomatosis (MC) originating from non-haematological tumours is a late event in the course of a malignant disease. MC must be suspected in patients with disperse neurological symptoms from at least two of the following three parts of the central nervous system: the brain, the cranial nerves, and the spinal cord, and if a discrepancy between symptoms and objective findings is found. A suspicion of MC must be confirmed by lumbar puncture and/or MR with Gadolinium in patients where a confirmation of MC will lead to active therapy. Therapy depends on tumour type, performance status of the patient, and present status of the malignant disease. Patients with good performance status and with a chemo-sensitive tumour are offered a combination of radiotherapy and chemotherapy. Median survival is one to three months and active therapy does not prolong survival with certainty. Therefore, therapy primarily aims at an improvement of quality of life for the patient.

Breast Neoplasms↗

PubMed1995

A phase 2 trial of ifosfamide/mesna as salvage therapy in patients with ovarian cancer refractory to or relapsing after prior platinum-containing chemotherapy.

Continuous 24-hr infusion of ifosfamide (IFX) with mesna was studied in 19 patients with advanced epithelial ovarian cancer refractory to or recurrent after platinum-containing chemotherapy. The patients received IFX 5 g/m2 as a 24-hr i.v. infusion. Mesna (total dose 8 g/m2) was given i.v. 3 hr before, together with, and 0 and 6 hr after IFX infusion, respectively. Cytotoxic therapy was repeated every 4 weeks. Of 19 evaluable patients, none achieved a complete response, 2 showed a partial response, and 8 had stable disease. Median survival for all patients was 6 months, and median time to progression was 4 months. Toxicity was moderate. Leucopenia WHO grade III-IV was observed in 3 patients. Thrombocytopenia WHO grade III-IV was not observed. Nausea/vomiting WHO grade III-IV occurred in 8 patients. One patient experienced mild reversible confusion. No patients had macro-or microscopic hematuria and there was no deterioration of renal function. We conclude that IFX given as a 24-hr infusion is moderately well tolerated, but has only limited activity in patients with ovarian cancer refractory to or relapsing after prior platinum-containing chemotherapy.

Adult↗

PubMed1995

Irradiation of bone metastases in breast cancer patients: a randomized study with 1 year follow-up.

The results from a prospective randomized trial comparing two different radiation schedules for treatment of painful bone metastases in women with recurrent breast cancer are presented. A total of 217 patients with painful bone metastases were randomized to either 30 Grey (Gy) in ten fractions, five fractions a week (5F/W) or 15 Gy in three fractions 2F/W. The effect of treatment was evaluated by pain assessment, the radiological response and the degree of side-effects. The patients were rated at start of treatment and after 1, 3, 6 and 12 months. No difference between the two radiation regimes was found, neither in achieved pain relief, improvement in level of activity and medication, nor was there any difference in radiological response and side-effects from treatment. Both regimes resulted in a significant improvement in both pain score and level of activity 1 month after treatment, an improvement which persisted during the follow-up period. We conclude that 15 Gy given in three fractions 2F/W is as effective as 30 Gy in ten fractions 5F/W, but more convenient to the patient and of less cost to society.

Adult↗

PubMed1995

Is carboplatin and oral etoposide an effective and feasible regimen in patients with small cell lung cancer?

The combination of carboplatin and etoposide is an active and well-tolerated regimen in the treatment of small cell lung cancer (SCLC). The aim of the study was to confirm whether the efficacy could be maintained if etoposide was administered orally. 106 consecutive, unselected, and untreated patients with SCLC (limited disease (LD) 44; extensive disease (ED) 62) were treated with a combination of carboplatin 300 mg/m2 intravenously (i.v.) day 1 and etoposide 240 mg/m2 orally days 1-3 every 4 weeks for six courses or until progression. If oral treatment was inconvenient, i.v. etoposide (120 mg/m2 days 1-3) was allowed. Thoracic irradiation (45 Gy in 22 fractions, split course) was given after three courses of chemotherapy to 29 patients with LD. Objective response (complete and partial) was seen in 89% (confidence interval (CI) 75-97) of patients with LD and in 53% (CI 40-66) with ED. Complete response was seen in 41% (CI 26-57) of patients with LD and in 8% (CI 2-18) with ED. Median time to progression for responders was 11 months and 6 months for patients with LD and ED, respectively. Corresponding median survival was 15 months (range 1-45 months) and 8.5 months (0-26 months). Myelosuppression comprised the main toxicity. Leucopenia (WHO III-IV) was observed in 20% and thrombocytopenia (WHO III-IV) in 16% of the cases. One patient died of sepsis during leucopenia. Oral treatment was convenient for most patients and therapy well tolerated. However, 9 patients (20%; CI 9-36%) with LD and 26 patients (42%; CI 29-56%) with ED received at least part of the etoposide treatment i.v.. The present study shows that the combination of carboplatin and oral etoposide is active and well tolerated, and may be used on an outpatient basis in patients with small cell lung cancer.

Administration, Oral↗

PubMed1994

Nonhomologous DNA end joining in Schizosaccharomyces pombe efficiently eliminates DNA double-strand-breaks from haploid sequences.

Cells of higher eucaryotes are known to possess mechanisms of illegitimate recombination which promote the joining between nonhomologous ends of broken DNA and thus may serve as basic tools of double-strand-break (DSB) repair. Here we show that cells of the fission yeast Schizosaccharomyces pombe also contain activities of nonhomologous DNA end joining resembling the ones found in higher eucaryotes. Nonhomologous end joining activities were detected by transformation of linearized self-replicating plasmids in yeast cells employing a selection procedure which only propagates transformants carrying recircularized plasmid molecules. Linear plasmid substrates were generated by duplicate restriction cuts carrying either blunt ends or 3' or 5' protruding single strands (PSS) of 4 nt which were efficiently joined in any tested combination. Sequence analysis of joined products revealed that junctional sequences were shortened by 1 to 14 nt. Two mechanisms may account for junction formation (i) loss of terminal nucleotides from PSS tails to produce blunt ends which can be joined to abutting ends and (ii) interactions of DNA termini at patches of sequence homologies (1-4 bp) by formation of overlap intermediates which are subsequently processed. A general feature of the yeast joining system is that end joining can only be detected in the absence of sequence homology between the linear substrate and host genome. In the presence of homology, nonhomologous DNA end joining is efficiently competed by activities of homologous recombination.

Base Sequence↗

PubMed1994

Nonhomologous DNA end joining of synthetic hairpin substrates in Xenopus laevis egg extracts.

Processes of DNA end joining are assumed to play a major role in the elimination of DNA double-strand breaks (DSB) in higher eucaryotic cells. Linear plasmid molecules terminated by nonhomologous restriction ends are the typical substrates used in the analysis of joining mechanisms. However, due to their limited structural variability, DSB ends generated by restriction cleavage cover probably only part of the total spectrum of naturally occurring DSB termini. We therefore devised novel DNA substrates consisting of synthetic hairpin-shaped oligonucleotides which permit the construction of blunt ends and 5'- or 3'-protruding single-strands (PSS) of arbitrary sequence and length. These substrates were tested in extracts of Xenopus laevis eggs known to efficiently join linear plasmids bearing nonhomologous restriction termini (Pfeiffer and Vielmetter, 1988). Sequences of hairpin junctions indicate that the short hairpins are joined by the same mechanisms as the plasmid substrates. However, the bimolecular DNA end joining reaction was only detectable when both hairpin partners had a minimal duplex stem length of 27bp and their PSS-tails did not exceed 10nt.

Animals↗

PubMed1994

Resolution and conservation of mismatches in DNA end joining.

DNA end joining is a major pathway for the elimination of double-strand breaks from chromosomal DNA of higher eucaryotic cells. Extracts of Xenopus laevis eggs rejoin such breaks even when their short single-stranded termini are expected to form imperfectly matched overlaps. However, end-joined products cloned in Escherichia coli, necessarily give rise to perfectly matched products. Therefore it has not been possible to determine whether the end joining process creates mismatched products, perfectly matched (resolved) products or both. To investigate whether mismatch resolution was the result of the X. laevis end joining process or of activities of the bacterial host we used denaturing gradient gel electrophoresis to analyse joined products. We found that the end joining process does include mismatch resolution, the degree of which varies with regard to the nature of the original overlap structure. Mismatches 3' to a gap are completely resolved, mismatches 3' to a nick and 5' to a nick or gap are resolved to some extent but are generally conserved. Mismatches between base matches are always conserved. These findings suggest competing processes of ligation, DNA fill-in synthesis or exonucleolytic excision of mismatched bases next to a gap or nick. At mismatches 3' to a nick the probability of ligation is greater than that of excision while at mismatches 3' to a gap the probability of excision is greater than elongation of a given mismatch. At mismatches 5' to nicks or gaps it appears that ligation or elongation and ligation, respectively, are the most probable pathways but products resulting from mismatch excision, elongation and ligation are also detected.

Animals↗

PubMed1994

Mechanisms of overlap formation in nonhomologous DNA end joining.

Rejoining of nonhomologous DNA termini plays a central role in processes of illegitimate recombination. In Xenopus egg extracts, DNA ends with noncomplementary 4-nucleotide antiparallel single-strand protrusions are assumed to be joined by formation of short mismatched overlap intermediates. The extents of these overlaps may be set by single fortuitously matching base pairs and determine the patterns of subsequent gap filling and nick ligation. Under conditions of alternative overlap settings, rules for the most probable joining pathway and the effects of mismatches on junction formation were analyzed. We show that in certain cases, fill-in and ligation converting overlap intermediates into covalently closed junctions may proceed in the presence of unrepaired mismatches, whereas in other cases, completion of junction formation is preceded by removal of mismatches. Results are discussed in relation with "alignment" proteins postulated to structurally support overlap heteroduplexes during junction formation.

Animals↗

PubMed1993

Radiation-induced brachial plexopathy: neurological follow-up in 161 recurrence-free breast cancer patients.

PURPOSE: The purpose was to assess the incidence and clinical manifestations of radiation-induced brachial plexopathy in breast cancer patients, treated according to the Danish Breast Cancer Cooperative Group protocols. METHODS AND MATERIALS: One hundred and sixty-one recurrence-free breast cancer patients were examined for radiation-induced brachial plexopathy after a median follow-up period of 50 months (13-99 months). After total mastectomy and axillary node sampling, high-risk patients were randomized to adjuvant therapy. One hundred twenty-eight patients were treated with postoperative radiotherapy with 50 Gy in 25 daily fractions over 5 weeks. In addition, 82 of these patients received cytotoxic therapy (cyclophosphamide, methotrexate, and 5-fluorouracil) and 46 received tamoxifen. RESULTS: Five percent and 9% of the patients receiving radiotherapy had disabling and mild radiation-induced brachial plexopathy, respectively. Radiation-induced brachial plexopathy was more frequent in patients receiving cytotoxic therapy (p = 0.04) and in younger patients (p = 0.04). The clinical manifestations were paraesthesia (100%), hypaesthesia (74%), weakness (58%), decreased muscle stretch reflexes (47%), and pain (47%). CONCLUSION: The brachial plexus is more vulnerable to large fraction size. Fractions of 2 Gy or less are advisable. Cytotoxic therapy adds to the damaging effect of radiotherapy. Peripheral nerves in younger patients seems more vulnerable. Radiation-induced brachial plexopathy occurs mainly as diffuse damage to the brachial plexus.

Adult↗

PubMed1993

Endonuclease VII of phage T4 triggers mismatch correction in vitro.

The reactivity of endonuclease VII (gp49 of phage T4) with DNA-loops of eight, four, or one nucleotide, or any of 12 possible base mismatches was tested in vitro. Endonuclease VII introduces double-strand breaks by nick and counter-nick within six nucleotides 3' from the mispairings. High relative cleavage efficiencies at mismatches in heteroduplexes correlate with their decreased thermal stability and vice versa. A delay between nick and counter-nick was sufficient to allow T4 DNA-polymerase and T4 DNA-ligase to correct a C/C-mismatch in vitro, thereby saving the DNA from double-strand breakage. Very short repair tracks of three to four nucleotides mapped between the mismatch and one of the formerly induced nicks, which were subsequently sealed by DNA ligase.

Bacteriophage T4↗

PubMed1993

Use of DNA end joining activity of a Xenopus laevis egg extract for construction of deletions and expression vectors for HIV-1 Tat and Rev proteins.

We have developed a cloning strategy which combines conventional T4 DNA ligation with the highly efficient nonhomologous DNA end joining (EJ) activity of an extract from Xenopus laevis eggs. The nonhomologous EJ activity allowed the rapid construction of deletion mutants by the intramolecular rejoining of nonhomologous DNA ends generated for the purpose of deleting restriction fragments from the vector. The combined use of T4 DNA ligase for intermolecular ligation and X. laevis egg extracts for intramolecular nonhomologous EJ proved to be a powerful tool, as demonstrated here for the construction of expression vectors for HIV-1 Tat and Rev.

Animals↗

PubMed1993

Membrane-associated replication of an unencapsidated double-strand RNA of the fungus, Cryphonectria parasitica.

Fungal vesicles isolated from a hypovirulent strain (EP113) of the chestnut blight fungus, Cryphonectria parasitica, contained double-stranded RNA and possessed an RNA-dependent RNA polymerase activity which was absent in comparable preparations from dsRNA-free vesicles of a virulent strain (EP 155). RNA polymerase activity remained associated with hypovirulent vesicles when these were sedimented through a 10 to 40% sucrose gradient and the polymerase activity coincided with the peak of dsRNA content. Incorporation of [32P]-UTP into RNA was proportional to the amount of vesicles present in the reaction mixture. Enzyme activity was dependent upon the presence of dsRNA-containing vesicles, Mg2+ and the four ribonucleotide triphosphates, and was insensitive to inhibitors of DNA-dependent RNA polymerases. The optimum temperature for polymerase activity was 30 degrees, and temperatures higher than 35 degrees inactivated the enzyme. Treatment of vesicles with low concentrations of detergent led to a two- to threefold increase in the rate of RNA synthesis. The RNA polymerase products, synthesized in vitro, hybridized specifically with C. parasitica genomic dsRNAs. Hybridization to single-stranded cDNA clones containing inserts of the terminal domains of the homopolymer and heteropolymer ends of the dsRNA showed that the reaction products were full-length copies of both strands of the dsRNA. Single-stranded RNA synthesis was asymmetrical, with greater than 80% of the polymerase products being of positive polarity. It can be estimated that in the fungal vesicles isolated from hypovirulent C. parasitica, transcription of the dsRNA into mRNA for translation is in the order of two- to eightfold more active than replication. On the basis of our results and of the evidence accumulated so far, we suggest that the replication strategy employed by the hypovirulence-associated dsRNA is following that of positive-strand RNA viruses.

Ascomycota↗

PubMed1993

Decreased efficacy of cyclophosphamide, epirubicin and 5-fluorouracil in metastatic breast cancer when reducing treatment duration from 18 to 6 months.

The impact of treatment duration on survival and progression-free survival is uncertain in metastatic breast cancer. In this trial 359 patients were randomised to receive cyclophosphamide, epirubicin and 5-fluorouracil (CEF) once every 3 weeks for a maximum of 18 months or identical chemotherapy for a maximum of 6 months. Following progressive disease (PD) or severe toxicity CEF was discontinued before the scheduled maximum duration. A second series of CEF continued for a maximum of 12 months was offered to patients with PD more than 3 weeks after completing a maximum of 6 months of CEF. Both groups received tamoxifen (30 mg daily) until PD, and premenopausal patients also received ovarian irradiation. After 6 months 254 evaluable patients were unprogressive. Survival and progression-free survival were significantly longer in 127 patients continuing CEF than in 127 patients interrupting CEF at 6 months (chi 2 = 17.6, P = 0.00003 and chi 2 = 4.7, P = 0.03, respectively). The results of the second series of CEF were discouraging with only one complete response in 44 evaluable patients. In conclusion, prolonged chemotherapy for 18 months is superior to identical chemotherapy for 6 months in the treatment of metastatic breast cancer.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1993

Unusual structure of the double-stranded RNA associated with the '447' cytoplasmic male sterility in Vicia faba.

The 16.7 kbp dsRNA specific to the '447' cytoplasmic male sterility (CMS) line of Vicia faba was labelled in vitro with [alpha-32P]ATP and poly(A) polymerase, and by T4 RNA ligase-mediated addition of [32P]pCp. Analysis of the reaction products under denaturing conditions revealed in both cases extensive labelling of a 4.5 kb ssRNA, already detected in previous experiments in which the RNA-dependent RNA polymerase associated with the dsRNA was allowed to pursue RNA synthesis on preinitiated complexes. Mobility shift analysis of total pCp-labelled dsRNA revealed not two but three different 3' termini. The most prominent sequencing pattern corresponded to the 4.5 kb ssRNA, indicating that this RNA species has a preferentially accessible, free 3' OH extremity. Northern blot analysis of the denatured dsRNA confirmed that the 4.5 kb ssRNA is a subgenomic mRNA and detected its counterpart of about 12 kb. Nearly all 16.7 kbp dsRNA molecules featured an interrupted positive-sense strand, indicating a marked prevalence of transcription over replication complexes. This unusual strategy of transcription by a strand displacement mechanism, following initiation at an internal discontinuity, is compared with that of other dsRNA viruses or defective viruses, and is discussed in relation to the expression of the CMS trait.

Base Sequence↗

PubMed1993

Surgical management of intraluminal carotid thrombi.

The most suitable treatment for intraluminal carotid thrombi remains still a much debated question. Some authors have reported a lower morbidity in patients treated with anticoagulant or antiplatelet therapy; on the other side, urgent or delayed surgery is burdened with a high risk of perioperative stroke. Over 11 years (october 1981-november 1992) 602 surgical revascularizations on epi-aortic vessels have been performed at Vascular Surgery Unit of Udine Regional Hospital. Only 2 cases of intraluminal carotid thrombi were observed: both fulfilled the angiographic requirements for endovasal filling defect, surrounded by contrast medium, adherent to posterior wall and extending to distal internal carotid artery. First patient suffered a TIA 20 days before surgery, the second one a previous major stroke contralateral to the thrombus. The former was given preoperatively a medical anticoagulant treatment (warfarin). At operation we discovered a nearly complete resolution of the thrombus: only its adherent base was still present. Therefore we performed a routine endarterectomy and a PTFE patch angioplasty. The latter case reported had no preliminary medical treatment; a thrombus extending from carotid bulbus to external and internal carotid was detected and then removed without any distal embolization. Arteriotomy was closed by Dacron Velour patch angioplasty. No perioperative stroke occurred in both cases: our second patient showed a partial resolution of his motility deficit. According to our limited experience, delayed surgical treatment of intraluminal carotid thrombi seems not to be affected with higher risk of perioperative stroke than prophylactic carotid endarterectomy.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed1992

Intravenous clodronate for the treatment of hypercalcaemia in breast cancer patients with bone metastases--a prospective randomised placebo-controlled multicentre study.

In a double blind randomised multicentre study the effect of intravenous clodronate plus hydration was compared with placebo plus hydration in the treatment of hypercalcaemia in breast cancer patients with bone metastases. The patients were treated either with hydration plus clodronate 300 mg/day or hydration plus placebo, up to 7 days or until serum ionised calcium was below 1.4 mmol/l. 25 patients received clodronate and 19 placebo. A significant difference in favour of clodronate was observed in the time to reach normocalcaemia (P = 0.004) and in the number of patients achieving normocalcaemia (P = 0.0003). 17 patients of 21 evaluable patients on clodronate achieved normocalcaemia compared with 4 of 19 patients on placebo. The only adverse event clearly associated with clodronate was symptomatic hypocalcaemia in 1 patient. Thus, clodronate seems to be a safe and highly efficacious drug for the treatment of hypercalcaemia in breast cancer patients.

Adult↗

PubMed1992

Activation of a system for the joining of nonhomologous DNA ends during Xenopus egg maturation.

Mature Xenopus laevis eggs provide an elementary reaction system of illegitimate recombination which efficiently joins nonhomologous DNA ends (P. Pfeiffer and W. Vielmetter, Nucleic Acids Res. 16:907-924, 1988). Here we show that stage VI oocytes, known to express a system for homologous recombination (D. Carroll, Proc. Natl. Acad. Sci. USA 80:6902-6906, 1983), are completely devoid of this joining system. Nonhomologous DNA end-to-end joining, however, attains full activity only at an extremely late stage of egg maturation. Cycloheximide inhibition patterns indicate that nonhomologous joining activity is regulated at the G2 restriction point of the cell cycle. Implications of homologous and nonhomologous recombination activities during egg maturation are discussed.

Animals↗

PubMed1992

Cytotoxic treatment of metastatic breast cancer. Which drugs and drug combinations to use?

Although the optimal efficacy of cytotoxic therapy plateaued in the 1970s, no consensus yet exists regarding which cytotoxic combination to offer as first-line therapy for metastatic breast cancer. Comparison of a combination of CAF/CEF with other cytotoxic combinations reveals that an anthracycline-containing regimen not only increases response rate, but also improves time to progression and survival. Regarding appropriate duration of cytotoxic therapy, randomized trials indicate that therapy in excess of 6 months is beneficial. Although the main objective of cytotoxic therapy in patients with metastatic disease is to palliate symptoms at the least toxic cost, the finding that adjuvant cytotoxic therapy improves survival provides a clinical and ethical rational for continued research into new drugs and combinations in the hope that new strategies can be employed not only against metastatic breast cancer but may be applied with benefit also in the adjuvant situation.

Antineoplastic Agents↗