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Biomedical subjects

J Gehl

Publications and source records attributed to J Gehl.

15 recordsLinked to original sources
PubMed2003

Electroporation: theory and methods, perspectives for drug delivery, gene therapy and research.

Electroporation designates the use of short high-voltage pulses to overcome the barrier of the cell membrane. By applying an external electric field, which just surpasses the capacitance of the cell membrane, transient and reversible breakdown of the membrane can be induced. This transient, permeabilized state can be used to load cells with a variety of different molecules, either through simple diffusion in the case of small molecules, or through electrophoretically driven processes allowing passage through the destabilized membrane--as is the case for DNA transfer. Initially developed for gene transfer, electroporation is now in use for delivery of a large variety of molecules: From ions to drugs, dyes, tracers, antibodies, and oligonucleotides to RNA and DNA. Electroporation has proven useful both in vitro, in vivo and in patients, where drug delivery to malignant tumours has been performed. Whereas initial electroporation procedures caused considerable cell damage, developments over the past decades have led to sophistication of equipment and optimization of protocols. The electroporation procedures used in many laboratories could be optimized with limited effort. This review (i) outlines the theory of electroporation, (ii) discusses factors of importance for optimization of electroporation protocols for mammalian cells, (iii) addresses particular concerns when using electroporation in vivo, e.g. effects on blood flow and considerations regarding choice of electrodes, (iv) describes DNA electrotransfer with emphasis on use in the in vivo setting, and (v) sums up data on safety and efficacy of electroporation used to enhance delivery of chemotherapy to tumours in cancer patients.

Animals↗
PubMed2000

Importance of association between permeabilization and electrophoretic forces for intramuscular DNA electrotransfer.

Gene transfer using electrical pulses is a rapidly expanding field. Many studies have been performed in vitro to elucidate the mechanism of DNA electrotransfer. In vivo, the use of efficient procedures for DNA electrotransfer in tissues is recent, and the question of the implied mechanisms is largely open. We have evaluated the effects of various combinations of square wave electric pulses of variable field strength and duration, on cell permeabilization and on DNA transfection in the skeletal muscle in vivo. One high voltage pulse of 800 V/cm, 0.1 ms duration (short high pulse) or a series of four low voltage pulses of 80 V/cm, 83 ms duration (long low pulses) slightly amplified transfection efficacy, while no significant permeabilization was detected using the (51)Cr-EDTA uptake test. By contrast, the combination of one short high pulse followed by four long low pulses led to optimal gene transfer efficiency, while inducing muscle fibers permeabilization. These results are consistent with additive effects of electropermeabilization and DNA electrophoresis on electrotransfer efficiency. Finally, the described new combination, as compared to the previously reported use of repeated identical pulses of intermediate voltage, leads to similar gene transfer efficiency, while causing less permeabilization and thus being likely less deleterious. Thus, combination of pulses of various strengths and durations is a new procedure for skeletal muscle gene transfer that may represents a clear improvement in view of further clinical development.

Animals↗
PubMed2000

Efficient palliation of haemorrhaging malignant melanoma skin metastases by electrochemotherapy.

Electric pulses can cause transient permeabilization of cell membranes (electroporation) and this can be utilized to increase the uptake of chemotherapy (electrochemotherapy). Preclinical studies have shown that in vivo electroporation causes transient shut down of blood flow both in normal and, in particular, malignant tissues. We report the successful palliation of a malignant melanoma patient with bleeding skin metastases using electrochemotherapy. In an on-going study of combined electrochemotherapy and low dose interleukin-2, one patient with bleeding skin metastases was included. Nine skin metastases, of which seven were ulcerated, were treated. After intratumoral bleomycin injection, needle electrodes with two arrays 4 mm apart were inserted into the tumours. Eight square wave electric pulses each 99 micros in duration and with an applied voltage to electrode distance ratio of 1.2 kV/cm were administered. In all the treated lesions, bleeding immediately stopped on administration of the electric pulses and did not recur. The treated metastases developed crusts and the lesions healed in a matter of weeks. Treatments were given under local anaesthesia, lasted a few minutes, and patient discomfort was brief and modest. In conclusion, we propose that electrochemotherapy should be considered for the palliation of haemorrhaging metastases as it is an efficient, tolerable, brief, outpatient, once-only treatment.

Aged↗
PubMed1999

In vivo electroporation of skeletal muscle: threshold, efficacy and relation to electric field distribution.

In vivo electroporation is increasingly being used to deliver small molecules as well as DNA to tissues. The aim of this study was to quantitatively investigate in vivo electroporation of skeletal muscle, and to determine the threshold for permeabilization. We designed a quantitative method to study in vivo electroporation, by measuring uptake of (51)Cr-EDTA. As electrode configuration influences electric field (E-field) distribution, we developed a method to calculate this. Electroporation of mouse muscle tissue was investigated using either external plate electrodes or internal needle electrodes placed 4 mm apart, and eight pulses of 99 micros duration at a frequency of 1 Hz. The applied voltage to electrode distance ratio was varied from 0 to 2.0 kV/cm. We found that: (1) the threshold for permeabilization of skeletal muscle tissue using short duration pulses was at an applied voltage to electrode distance ratio of 0.53 kV/cm (+/-0.03 kV/cm), corresponding to an E-field of 0.45 kV/cm; (2) there were two phases in the uptake of (51)Cr-EDTA, the first indicating increasing permeabilization and the second indicating beginning irreversible membrane damage; and (3) the calculated E-field distribution was more homogeneous for plate than for needle electrodes, which was reflected in the experimental results.

Animals↗
PubMed1999

Determination of optimal parameters for in vivo gene transfer by electroporation, using a rapid in vivo test for cell permeabilization.

In vivo gene transfer to muscle tissue by electroporation can produce long-term, high-level gene expression. In the present study, we report quantitative results on muscle fiber permeabilization using Cr(51)-EDTA as a marker, and we analyze the influence of electric field strength, pulse duration, and pulse number. The comparison of these results to recently published data on gene transfer (Mir et al., P.N.A.S. (USA), 1999), using an identical experimental setup provides the basis for discussing the importance of the level of permeabilization for gene transfer. The threshold for permeabilization was determined by measuring uptake of Cr(51)-EDTA, and DNA transfer was optimal for field strengths just above the threshold for permeabilization. This means that when designing in vivo electric-field-mediated gene transfer protocols for various tissues, determining the threshold for permeabilization using a rapid test such as incorporation of Cr(51)-EDTA, can be used to predict the optimal window for gene transfer.

Animals↗
PubMed1999

High-efficiency gene transfer into skeletal muscle mediated by electric pulses.

Gene delivery to skeletal muscle is a promising strategy for the treatment of muscle disorders and for the systemic secretion of therapeutic proteins. However, present DNA delivery technologies have to be improved with regard to both the level of expression and interindividual variability. We report very efficient plasmid DNA transfer in muscle fibers by using square-wave electric pulses of low field strength (less than 300 V/cm) and of long duration (more than 1 ms). Contrary to the electropermeabilization-induced uptake of small molecules into muscle fibers, plasmid DNA has to be present in the tissue during the electric pulses, suggesting a direct effect of the electric field on DNA during electrotransfer. This i.m. electrotransfer method increases reporter and therapeutic gene expression by several orders of magnitude in various muscles in mouse, rat, rabbit, and monkey. Moreover, i.m. electrotransfer strongly decreases variability. Stability of expression was observed for at least 9 months. With a pCMV-FGF1 plasmid coding for fibroblast growth factor 1, this protein was immunodetected in the majority of muscle fibers subjected to the electric pulses. DNA electrotransfer in muscle may have broad applications in gene therapy and in physiological, pharmacological, and developmental studies.

Animals↗
PubMed1998

Enhancement of cytotoxicity by electropermeabilization: an improved method for screening drugs.

Electropermeabilization (EPN), also termed electroporation, is a physical method to overcome the barrier of the cell membrane by applying short and intense electric pulses. It is the basis for a new cancer treatment modality, electrochemotherapy, where uptake of chemotherapeutics is enhanced by EPN. Preclinical and clinical trials have shown that application of electric pulses in vivo is feasible and that electrochemotherapy is highly efficient. The aim of this study was to develop an improved method of screening drugs on electropermeabilized versus non-electropermeabilized cells. In this study we describe an easy protocol which gives high cell viability, good reproducibility and a high rate of cell permeabilization. Cell cytotoxicity is simply determined by the MTT assay. Cell death due to the EPN procedure was less than 4% and more than 90% of cells were permeabilized. For daunorubicin, doxorubicin, etoposide and paclitaxel, no effect of EPN was found. For carboplatin and cisplatin the effect of EPN was a factor 3 and 2.3, respectively, on the IC50 (inhibitory concentration 50%). For bleomycin we found a dramatic effect of EPN of the magnitude of a factor 300 on the IC50. In conclusion, we have established a new, easy and reliable protocol to test new drugs for cytotoxicity with or without the limitations of the cell membrane. Our data support the role of bleomycin as the drug of choice for electrochemotherapy.

Animals↗
PubMed1996

Combined doxorubicin and paclitaxel in advanced breast cancer: effective and cardiotoxic.

BACKGROUND: Paclitaxel has shown activity in metastatic breast cancer, including anthracycline-resistant breast cancer. The efficacy, toxicity and optimal scheduling of the combination of the two drugs needs to be defined. PATIENTS AND METHODS: Thirty women with advanced breast cancer who had undergone at most one prior adjuvant chemotherapy regimen, were treated at three different dose levels with doxorubicin (50, 60 and 60 mg/m2) followed 30 minutes later by paclitaxel (155, 175 and 200 mg/m2, respectively) every 3 weeks. RESULTS: The overall response rate was 83% (95% CI: 64-94), with 24% of patients achieving CR. The median response duration for complete responders was 11 months (range 4-14+) and median survival 18 months (range 3-28+). Two hundred sixty-five treatment courses were given (median 9, range 3-13) and the median cumulative dose of doxorubicin was 369 mg/m2 (range 114-550). The main toxicities were neutropenia, parestesia, nausea/vomiting, alopecia, myalgia and cardiotoxicity. Fifteen patients (50%) had reductions of left ventricular ejection fraction of below normal levels and 6 of these patients (20%) developed congestive heart failure. CONCLUSION: The combination of doxorubicin and paclitaxel is highly active, but is accompanied by the dose-limiting toxic effects of neutropenia, neuropathy and cardiotoxicity.

Adult↗
PubMed1996

Paclitaxel and doxorubicin, a highly active combination in the treatment of metastatic breast cancer.

The activity of single-agent paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) has been documented in untreated and previously treated metastatic breast cancer, including both patients with anthracycline-resistant disease and those with extensive pretreatment. Such activity has prompted investigations of the optimal doses and schedules of paclitaxel/doxorubicin combinations. With one exception, paclitaxel has been administered as either a 24- or a 3-hour infusion, while the administration times for doxorubicin vary from bolus injection to 72-hour infusion. Results of these completed phase I and II trials are reviewed. Also reported are two European trials that have achieved promising results. In Milan, a phase I/II trial has shown a preliminary response rate exceeding 90% in 32 chemotherapy-naive patients treated with an alternating schedule of paclitaxel given over 3 hours and intravenous bolus doxorubicin. At doses of paclitaxel 200 mg/m2 and doxorubicin 60 mg/m2, the dose-limiting toxicities were neutropenia, oral mucositis, myalgias, and peripheral neuropathy. Congestive heart failure occurred in six patients. A phase I/II study of a 30-minute doxorubicin infusion preceding a 3-hour paclitaxel infusion every 3 weeks in minimally pretreated patients also is reported. Of 29 patients evaluable for response, 17 have achieved partial responses and seven complete responses, for an overall response rate of 83% (95% confidence interval, 79% to 99%). Toxicities observed were grades 3 to 4 neutropenia and moderate paresthesias, nausea/vomiting, alopecia, myalgia, and mucositis. Cardiotoxicity also occurred, as 15 patients had a significant decrease in left ventricular ejection fraction measured by isotope cardiography. Six of these developed congestive heart failure. This effect has been observed only in studies using short infusions of both drugs, and it is now being investigated whether lowering the peak doxorubicin concentration will preclude it.

Antibiotics, Antineoplastic↗
PubMed1996

Doxorubicin and paclitaxel, a highly active combination in the treatment of metastatic breast cancer.

Paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) is active against advanced breast cancer and anthracycline-resistant breast cancer. We assessed the efficacy and toxicity of doxorubicin followed by a 3-hour infusion of paclitaxel in women with advanced breast cancer. Participants could have received at most one prior adjuvant chemotherapy regimen, but no previous exposure to anthracyclines or taxanes was permitted. The patients were treated every 3 weeks with doxorubicin (50 or 60 mg/m2) followed 30 minutes later by paclitaxel (155, 175, or 200 mg/m2). After reaching the maximum cumulative doxorubicin dose, treatment could be continued with paclitaxel alone. Thirty women were included, of whom 29 were evaluable for response. The overall response rate was 83% (95% confidence interval, 64% to 94%), with 24% of patients attaining complete remission. Median response duration for complete responders was 8+ months (range, 4 to 13 months) and median time to progression was 9 months (range, 2 to 18 months). Main toxicities were neutropenia, paresthesia, nausea/vomiting, alopecia, myalgia, and cardiotoxicity. In 15 patients (50%), the left ventricular ejection fraction decreased to below normal levels; six patients (20%) developed congestive heart failure. In conclusion, the combination of doxorubicin and paclitaxel is highly active; dose-limiting toxicities are neutropenia, neuropathy, and cumulative cardiotoxicity.

Adult↗
PubMed1996

Paclitaxel and doxorubicin in metastatic breast cancer.

For the past decades the anthracyclines have been regarded as among the most active drugs for the treatment of metastatic breast cancer. However, the 5-year survival rate in patients with stage IV breast cancer continues to be below 20%, and new active drugs and drug combinations clearly must be explored. Paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) has been demonstrated to be highly effective in treating patients with advanced breast cancer, including those with anthracycline-resistant breast cancer, a fact that has led to efforts to combine paclitaxel and anthracyclines. Several studies aiming to define the optimal dose and schedule of combination paclitaxel/doxorubicin have now been completed or are ongoing. Phase I/II studies have yielded encouraging preliminary response rates but quite variable toxicity profiles depending on the schedule used. These clinical trials involving combination paclitaxel/doxorubicin are reviewed, with special emphasis on the short-infusion trials.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1995

Treatment of metastatic breast cancer with paclitaxel and doxorubicin.

The activity of single-agent paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) against untreated and previously treated metastatic breast cancer (documented in anthracycline-resistant disease and in extensively pretreated patients as well) has prompted investigations of the optimal doses and schedules of paclitaxel/doxorubicin combinations. With one exception, paclitaxel has been administered in either a 24- or a 3-hour infusion, while the administration times for doxorubicin vary from bolus injection to a 72-hour infusion. Results of these completed phase I and II trials are reviewed. Also reported are two ongoing European trials that have achieved promising preliminary results. In Milan, a phase I trial has achieved a preliminary response rate exceeding 90% in 30 chemotherapy-naive patients treated with an alternating schedule of paclitaxel over 3 hours and intravenous bolus doxorubicin. At doses of paclitaxel 200 mg/m2 and doxorubicin 60 mg/m2, the dose-limiting toxicity is leukopenia and mucositis. Furthermore, congestive heart failure has occurred in six patients. We are conducting a phase I/II study in minimally pretreated patients, with a 30-minute doxorubicin infusion preceding a 3-hour paclitaxel infusion every 3 weeks. Of 24 patients evaluable for response, five have achieved partial responses and three complete responses. (Another five partial and two complete responses need confirmation.) Of the two dose levels now given, all responses occurred at the higher paclitaxel/doxorubicin level, 175 and 60 mg/m2, respectively. Despite grades 3 and 4 neutropenia in 31% and 60% of courses, respectively, only six patients have been hospitalized for febrile neutropenia. Of concern, the left ventricular ejection fraction has decreased to below normal in six patients and two have developed symptomatic congestive heart failure. Whether lowering the peak doxorubicin concentration will preclude this effect, which has been observed only in the studies using short infusions of both drugs, is under investigation.

Antibiotics, Antineoplastic↗
PubMed1988

The gastric acid secretagogue gastrin-releasing peptide and the inhibitor oxyntomodulin do not exert their effect directly on the parietal cell in the rat.

Previous studies suggested that gastrin-releasing peptide (a neuropeptide found in rat oxyntic mucosa) and oxyntomodulin (a glucagon-containing peptide of mammalian gut) could directly affect the acid secretion of the parietal cells. We therefore studied their effect on gastric acid production in vitro by measuring [14C]-aminopyrine accumulation, a reliable index of H+ generation, in isolated rat parietal cells. However, neither gastrin-releasing peptide nor oxyntomodulin influenced basal acid secretion or histamine-stimulated gastric acid secretion. Electron-microscopic studies of unstimulated and histamine-stimulated parietal cells confirmed that the cells retained the normal morphology of intracellular organelles and that the cells responded to physiological stimulation by marked expansion of the intracellular canaliculi.

Aminopyrine↗
PubMedDate not supplied

Traffic-related air pollution: exposure and health effects in Copenhagen street cleaners and cemetery workers.

This questionnaire-based study found a significantly higher prevalence of chronic bronchitis, asthma, and several other symptoms in 116 Copenhagen street cleaners who were exposed to traffic-related air pollution at levels that were slightly lower than the 1987 World Health Organization-recommended threshold values, compared with 115 Copenhagen cemetery workers exposed to lower pollution levels. Logistic regression analysis, controlling for age and smoking, was conducted, and odds ratios and 95% confidence intervals were calculated to be 2.5 for chronic bronchitis (95% confidence interval = 1.2-5.1), 2.3 for asthma (95% confidence interval = 1.0-5.1), and 1.8-7.9 for other symptoms (95% confidence interval = 1.0-28.2). Except for exposure to air pollution, the two groups were comparable, i.e., they had similar terms of employment and working conditions. The exposure ranges during an 8-h work day, averaged from readings taken at five monitored street positions, were: 41-257 ppb nitric oxide (1-h max: 865 ppb); 23-43 ppb nitrogen dioxide (1-h max: 208 ppb); 1.0-4.3 ppm carbon monoxide (8-h max: 7.1 ppm); 14-28 ppb sulfur dioxide (1-h max: 112 ppb); and 10-38 ppb ozone (1-h max: 72 ppb).

Adult↗