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PubMed2006

The Precautionary Principle must be guided by EMF research.

Regulatory action based on the Precautionary Principle is generally guided by the results of epidemiology studies. Even though laboratory research on electromagnetic fields (EMF) has supplied much relevant information and continues to do so, it is often overlooked. Laboratory research has shown that EMF of many frequencies stimulate many biological systems, and at low thresholds of both field strength and duration. It has also shown that EMF stimulate protein synthesis in cells and accelerate electron transfer reactions. In the last few years, important practical insights have been provided by the research on the cellular stress response, where the same specific biological response is induced in cells by both ELF (power frequency) and RF (radio frequency) fields, despite the very different energy levels. Since this protective biological response is not determined by the level of energy absorbed, safety standards based on the best available biological evidence must (1) recognize non thermal protective responses and (2) include cumulative exposures across the EM spectrum.

DNA↗
PubMed2001

An in vitro system for the study of ultrasound contrast agents using a commercial imaging system.

An in vitro system for the investigation of the behaviour of contrast microbubbles in an ultrasound field, that provides a full diagnostic range of settings, is yet to be presented in the literature. The evaluation of a good compromise of such a system is presented in this paper. It is based on (a) an HD13000 ATL scanner (Bothell, WA, USA) externally controlled by a PC and (b) on the use of well-defined reference materials. The suspensions of the reference ultrasonic scattering material are placed in an anechoic tank. The pulse length ranges from 2 to 10 cycles, the acoustic pressure from 0.08 to 1.8 MPa, the transmit frequency from 1 to 4.3 MHz, and the receive frequency from 1 to 8 MHz. The collection of 256 samples of RF data, at an offset distance from the transducer face, was performed at 20 MHz digitization rate, which corresponds to approximately 1 cm depth in water. Two particle suspensions are also presented for use as reference scatterers for contrast studies: (a) a suspension of Orgasol (ELF Atochem, Paris, France) particles (approximately 5 microm mean diameter) and (b) a suspension of Eccosphere (New Metals & Chemicals Ltd, Essex, UK) particles (approximately 50 microm mean diameter). A preliminary experiment with the contrast agent Definity (DuPont Pharmaceutical Co, Waltham, MA) showed that the above two materials are suitable for use as a reference for contrast backscatter.

Contrast Media↗
PubMed2004

Viscoelastic characterization of in vitro canine tissue.

Mechanical properties of biological tissues are of interest for assessing the performance of elastographic methods that evaluate the stiffness characteristics of tissue. The mechanical properties of interest include the frequency-dependent complex moduli, storage and loss moduli of tissues. Determination of the mechanical properties of biological tissues is often limited by proper geometry of the sample, as well as homogeneity of the stress-strain relationship. Measurements were performed on in vitro canine liver tissue specimens, over a frequency range from 0.1 to 400 Hz. Tests were conducted using an EnduraTEC ELF 3200, a dynamic testing system for determining the mechanical properties of materials. Both normal tissues and thermal lesions prepared by radio frequency ablation were tested. Experiments were conducted by uniaxially compressing tissue samples using Plexiglas platens larger than the specimens and measuring the load response. The resulting moduli spectra were then fit to a modified Kelvin-Voigt model, called the Kelvin-Voigt fractional derivative model. The data agree well with the model and in comparing the results from the normal tissue with that of the thermal lesions, the concept of a complex modulus contrast is introduced and its applications to elastography are discussed.

Animals↗
PubMed1994

Regulation of the urokinase gene by the retinoblastoma protein.

The promoter of the human urokinase plasminogen activator (uPA) gene contains a sequence identical with the retinoblastoma control element (RCE) of the murine c-fos gene, as well as several Sp1 binding sites. In a number of cell lines, the uPA promoter is activated during enforced expression of the retinoblastoma protein, pRB. Electrophoretic mobility-shift assays revealed that the RCE sequence of the uPA gene forms only one specific DNA-protein complex that does not contain pRB. The formation of the RCE-protein complex can be inhibited by 20 molar excess of the unlabeled RCE sequences and by 5 molar excess of the unlabeled E2F binding site. The RCE of the human uPA gene interacts specifically with a protein, which appears to be distinct from members of the E2F family of proteins, Sp1, ATF2, and Elf-1, which are all transcription factors shown to be regulated by pRB.

Animals↗
PubMed1998

Lack of a co-promoting effect of a 60 Hz magnetic field on skin tumorigenesis in SENCAR mice.

It has been proposed that extremely low frequency (ELF) magnetic fields may enhance tumorigenesis through a co-promotional mechanism. This hypothesis has been further tested using the two-stage model of mouse skin carcinogenesis, i.e. 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced promotion of skin tumors in mice initiated by a single subcarcinogenic dose of 7,12-dimethylbenz[a]anthracene. Experimentation described herein utilized the SENCAR mouse and examined the effect of a magnetic field on skin tumor promotion induced by three different doses of TPA within its dose-response range, i.e. 0.85, 1.70 or 3.40 nmol, administered twice per week. SENCAR mice (56/treatment group) were exposed to a 60 Hz magnetic field having a flux density of 2 mT for 6 h/day for 5 days/week and compared with mice exposed to the ambient magnetic field. Tumor incidence and multiplicity were monitored weekly for 23 weeks of TPA promotion. Statistical evaluation of the effects of the magnetic field on tumor incidence and multiplicity did not reveal any statistically significant effects; thus, within the sensitivity limits imposed by the animal model and the exposure parameters employed, no promotional or co-promotional effect of a 2 mT magnetic field on skin tumor development in SENCAR mice could be demonstrated.

Animals↗
PubMed2002

Establishing the transcriptional programme for blood: the SCL stem cell enhancer is regulated by a multiprotein complex containing Ets and GATA factors.

Stem cells are a central feature of metazoan biology. Haematopoietic stem cells (HSCs) represent the best-characterized example of this phenomenon, but the molecular mechanisms responsible for their formation remain obscure. The stem cell leukaemia (SCL) gene encodes a basic helix-loop-helix (bHLH) transcription factor with an essential role in specifying HSCs. Here we have addressed the transcriptional hierarchy responsible for HSC formation by characterizing an SCL 3' enhancer that targets expression to HSCs and endothelium and their bipotential precursors, the haemangioblast. We have identified three critical motifs, which are essential for enhancer function and bind GATA-2, Fli-1 and Elf-1 in vivo. Our results suggest that these transcription factors are key components of an enhanceosome responsible for activating SCL transcription and establishing the transcriptional programme required for HSC formation.

Amino Acid Sequence↗
PubMed2006

Evaluation of bacterial kill when modelling the bronchopulmonary pharmacokinetic profile of moxifloxacin and levofloxacin against parC-containing isolates of Streptococcus pneumoniae.

OBJECTIVES: The increasingly recognized prevalence of first-step parC mutants in Streptococcus pneumoniae and the development of de novo resistance while on fluoroquinolone therapy are of concern. Previous work by our group demonstrated the ability of moxifloxacin, but not levofloxacin, to eradicate parC mutants. The objective of this experiment was to determine whether these fluoroquinolone antibiotics provided equivalent bacterial kill when similar AUC/MICs were examined. METHODS: An in vitro pharmacodynamic model was used to simulate the epithelial lining fluid (ELF) concentrations following oral administration of levofloxacin 500 mg once daily and moxifloxacin 400 mg once daily in older adults. In addition, a range of AUC/MICs were also modelled, including levofloxacin 750 mg once daily. Five different S. pneumoniae containing first-step parC mutations and one isolate without mutations were tested for 48 h and time-kill curves were constructed. Samples at 0, 24 and 48 h were collected for phenotypic and genotypic profiling. HPLC was used to verify that target exposures were achieved. RESULTS: The isolate without a parC mutation displayed a 4 log reduction in cfu after treatment with levofloxacin 500 mg and did not select for resistance. In all five isolates containing first-step parC mutations, resistance emerged within 48 h with a > or =16-fold increase in MIC and the acquisition of a gyrA mutant. Increasing the exposure of levofloxacin to approximately 750 mg dose still led to > or =16-fold increase in MIC at 48 h in two of the four isolates containing parC mutations. On the other hand, moxifloxacin 400 mg sustained bacterial killing against the two isolates tested without the selection of resistant mutants. It appears that the critical AUC/MIC necessary to prevent the acquisition of resistance for levofloxacin is 200 and approximately 400 for moxifloxacin. CONCLUSIONS: Due to suboptimal exposures, once-daily oral regimens of levofloxacin at both 500 and 750 mg inconsistently led to bactericidal activity and the frequent acquisition of a second-step gyrA mutation in S. pneumoniae isolates already containing a first-step parC mutation. Conversely, once-daily moxifloxacin 400 mg provides exposures that vastly exceed the apparent efficacy breakpoint and did not select for second-step mutants until exposures were decreased 4-fold. As a result of these data and the emerging literature involving mutations in the pneumococcus, caution should be exercised when the respiratory fluoroquinolones are used to treat patients infected with S. pneumoniae suspected of having parC mutations.

Adult↗
PubMed1996

18S rRNA processing requires the RNA helicase-like protein Rrp3.

We report the identification of a new gene, RRP3 (rRNA processing), which is required for pre-rRNA processing. Rrp3 is a 60.9 kDa protein that is required for maturation of the 35S primary transcript of pre-rRNA and is required for cleavages leading to mature 18S RNA. RRP3 was identified in a PCR screen for DEAD box genes. DEAD box genes are part of a large family of proteins homologous to the eukaryotic transcription factor elF-4a. Most of these proteins are RNA-dependent ATPases and some of them have RNA helicase activity. This is the third yeast DEAD box protein that has been shown to be involved in rRNA assembly, but the only one required for the processing of 18S RNA. Mutants of the two other putative helicases, Spb4 and Drsl, both show processing defects in 25S rRNA maturation. In strains where Rrp3 is depleted, 35S precursor RNA is improperly processed. Cleavage normally occurs at sites A0O, Al and A2, but in the Rrp3 depletion stain cleavage occurs between A2 and B1. Rrp3 has been purified to homogeneity and has a weak RNA-dependent ATPase activity which is not specific for rRNA.

Adenosine Triphosphatases↗
PubMed1997

The CLUSTAL_X windows interface: flexible strategies for multiple sequence alignment aided by quality analysis tools.

CLUSTAL X is a new windows interface for the widely-used progressive multiple sequence alignment program CLUSTAL W. The new system is easy to use, providing an integrated system for performing multiple sequence and profile alignments and analysing the results. CLUSTAL X displays the sequence alignment in a window on the screen. A versatile sequence colouring scheme allows the user to highlight conserved features in the alignment. Pull-down menus provide all the options required for traditional multiple sequence and profile alignment. New features include: the ability to cut-and-paste sequences to change the order of the alignment, selection of a subset of the sequences to be realigned, and selection of a sub-range of the alignment to be realigned and inserted back into the original alignment. Alignment quality analysis can be performed and low-scoring segments or exceptional residues can be highlighted. Quality analysis and realignment of selected residue ranges provide the user with a powerful tool to improve and refine difficult alignments and to trap errors in input sequences. CLUSTAL X has been compiled on SUN Solaris, IRIX5.3 on Silicon Graphics, Digital UNIX on DECstations, Microsoft Windows (32 bit) for PCs, Linux ELF for x86 PCs, and Macintosh PowerMac.

Algorithms↗
PubMed1999

Late-flowering genes interact with early-flowering genes to regulate flowering time in Arabidopsis thaliana.

To investigate the genetic mechanisms regulating the transition from the vegetative to reproductive growth in Arabidopsis, double mutants between three different early-flowering mutants, early flowering 1-1, 2-1, 3-1, (elf 1-1, 2-1, 3-1) and five different late-flowering mutants, gi-1, ft-1, fwa-1, ld-1, and fca-9, were constructed and phenotypes analyzed. Double mutants in all combinations displayed the late-flowering phenotypes which resembled their respective late-flowering parents in both flowering time and the number of vegetative leaves produced. The results indicate that five late-flowering mutants are epistatic to all three early-flowering mutants tested here. This epistatic relationship suggests that ELF1, ELF2, and ELF3 genes function upstream of these five late-flowering genes no matter if they are functioning in autonomous or photoperiod pathways. These three early-flowering genes may negatively modify the activity of most late-flowering genes to influence the time of the vegetative-to-reproductive transition in Arabidopsis.

Arabidopsis↗
PubMed1999

Role of ets factors in the activity and endothelial cell specificity of the mouse Tie gene promoter.

The Tie gene encodes an endothelial cell receptor tyrosine kinase necessary for normal vascular development. The Tie gene promoter targets expression of heterologous genes specifically to endothelial cells in transgenic mice. Here we have characterized the promoter sequences critical for endothelial cell-specific activity in cultured cells and transgenic mice. Progressive deletions and site-directed mutations of the promoter showed that the critical endothelial cell-specific elements are an octamer transcription factor binding site and several Ets binding sites located in two clusters within 300 bp upstream of the major transcription initiation site. Among members of the Ets transcription factor family tested, NERF-2 (a novel transcription factor related to the ets factor ELF-1), which is expressed in endothelial cells, and ETS2 showed the strongest transactivation of the Tie promoter; ETS1 gave lower levels of stimulation and the other Ets factors gave little or no transactivation. Furthermore, the Tie promoter directed the production of high amounts of human growth hormone into the circulation of transgenic mice. The secreted amounts correlated with transgene copy number, being relatively insensitive to the effects of the transgene integration site. These properties suggest that Tie promoter activity is controlled by endothelial cell Ets factors and that it has potential for use in vectors for endothelial cell-specific gene expression.

Animals↗
PubMed2006

Regulation of c-jun mRNA expression in adult cardiocytes by MAP kinase interacting kinase-1 (MNK1).

Hypertrophic growth of adult myocardium is associated with increased expression of the early response gene c-jun. The purpose of this study was to determine whether eukaryotic initiation factor (elF) 4E (eIF4E) regulates translational efficiency of c-jun mRNA as measured by flux into polysomes. Adult feline cardiomyocytes in primary culture were treated with 0.2 microM 12-O-tetradecanoylphorbol 13-acetate (TPA), and c-jun mRNA was quantified in total, monosome, and polysome fractions by real-time polymerase chain reaction. After 1 h, TPA increased total c-jun mRNA by 10.5-fold. The corresponding flux into polysomes was significantly lower (5-fold). Adenoviral-mediated overexpression of either eIF4E or a nonphosphorylatable mutant (S209/A) did not affect total c-jun mRNA or its flux between monosomes and polysomes. Similar results were obtained following overexpression of the eIF4E kinase Mnk1. Thus, translational efficiency of c-jun mRNA was not affected by changes in activity or amount of eIF4E. In contrast, a kinase-deficient Mnk1 mutant significantly reduced total c-jun mRNA from 9.8-fold to 6.0-fold while flux between monosomes and polysomes remained constant. The decrease in total c-jun mRNA resulted from increased decay of c-jun mRNA incorporated into the polysomes. We conclude that Mnk1 activity stabilizes c-jun mRNA in polysomes independent of eIF4E phosphorylation.

Animals↗
PubMed1998

Phase I-II study of 5-fluorouracil, leucovorin, doxorubicin, methotrexate, and long-term oral etoposide (FLAME) in unresectable or metastatic gastric cancer.

The objective of this phase I-II study was to determine the efficacy and toxicity of combination chemotherapy with 5-fluorouracil, leucovorin, doxorubicin, methotrexate, and oral etoposide (FLAME) in patients with measurable unresectable or metastatic gastric cancer. Starting doses on the phase I study were as follows: methotrexate 50 mg/m2 intravenous bolus day 1; leucovorin 20 mg/m2 intravenous bolus days 2 through 4, starting 24 hours after the methotrexate dose; 5-fluorouracil 325 mg/m2 intravenous bolus 15 minutes after leucovorin days 2 through 4; doxorubicin 25 mg/m2 intravenous bolus day 8; and oral etoposide 50 mg/day for 14 days, starting on day 8. A new cycle started on day 28. A total of 42 patients were treated--10 patients in the phase I study and 32 patients in the phase II study. Dose-limiting toxicity was encountered in the phase I study on the second escalation step, when doxorubicin was escalated to 30 mg/m2 and 5-fluorouracil was escalated to 350 mg/m2. In the phase II study 28 patients (109 courses) were evaluable for toxicity. Neutropenia grade 3 or more was dose limiting and was documented in 12 patients (43%) during 22 treatment courses (20%). Neutropenia was associated with febrile neutropenia requiring hospitalization in four patients during five courses of therapy. Grade 3 stomatitis and grade 3 diarrhea was infrequent, documented in two patients (two courses) and three patients (four courses), respectively. All other toxicity was grade 1 and grade 2. The combined objective response rate in 38 evaluable patients entered in both studies was 23.3% (six partial responses and one complete response). Stable disease was documented in 15 patients (39.5%). The median survival for the 42 patients entered in both trials was 6.9 months (95% confidence interval, 5.9-8.5 months). The objective response rate and median survival for the combined group is comparable with that reported for the etoposide, leucovorin, and 5-fluorouracil (ELF), and 5-fluorouracil and methotrexate (FMTX) regimens in a recently reported, multicenter, phase III study.

Adenocarcinoma↗
PubMed2001

Parental occupational exposures to electromagnetic fields and radiation and the incidence of neuroblastoma in offspring.

We examined parental occupational exposures to electromagnetic fields and radiation and the incidence of neuroblastoma in offspring. Cases were 538 children diagnosed with neuroblastoma between 1992 and 1994 in the United States or Canada. Age-matched controls were selected by random-digit dialing. Occupational exposures to electrical equipment and radiation sources were classified by an industrial hygienist, and average exposures to extremely low frequency magnetic fields were estimated using a job exposure matrix. Maternal exposure to a broad grouping of sources that produce radiofrequency radiation was associated with an increased incidence of neuroblastoma (odds ratio = 2.8; 95% confidence interval = 0.9-8.7). Paternal exposure to battery-powered forklifts was positively associated with neuroblastoma (odds ratio = 1.6; 95% confidence interval = 0.8-3.2), as were some types of equipment that emit radiofrequency radiation (odds ratios congruent with 2.0); however, the broad groupings of sources that produce ELF fields, radiofrequency radiation, or ionizing radiation were not associated with neuroblastoma. Paternal average extremely low frequency magnetic field exposure >0.4 microTesla was weakly associated with neuroblastoma (odds ratio = 1.6; 95% confidence interval = 0.9-2.8), whereas maternal exposure was not. Overall, there was scant supportive evidence of strong associations between parental exposures in electromagnetic spectrum and neuroblastoma in offspring.

Case-Control Studies↗
PubMed1991

Perspectives in chemotherapy of advanced gastric cancer.

A review of recent phase II and III studies in advanced gastric carcinoma is presented. Several combination regimens have been developed with high activity in locally advanced and metastatic disease. Among them are etoposide plus adriamycin plus cisplatin (EAP), etoposide plus 5-fluorouracil plus leucovorin (ELF), continuous infusion 5-fluorouracil plus cisplatin and high dose methotrexate plus 5-fluorouracil plus adriamycin (FAMTX). In locally advanced disease a resectability rate of +/- 50% has been reported with these protocols. So far only FAMTX has demonstrated superiority compared with 5-fluorouracil, adriamycin and mitomycin (FAM), which regimen has been considered 'standard' treatment for many years. Randomized studies in which the other regimens are being more definitely assessed are underway.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1996

Chemotherapy of gastric cancer.

Patients with gastric adenocarcinomas have a poor prognosis. Because curative surgery is often impossible (metastatic disease) or extremely difficult (locally advanced tumors), and the majority of patients undergoing curative resection relapse, chemotherapy has been actively studied in gastric cancer. Many drugs have shown activity; however, single-agent chemotherapy failed to demonstrate increased survival benefit. Several combination regimens have been developed with high activity in locally advanced and metastatic disease. Among them are 5-fluorouracil (5-FU) plus high dose methotrexate plus doxorubicin (FAMTX), etoposide plus doxorubicin plus cisplatin (EAP), etoposide plus leucovorin plus 5-FU (ELF), and epirubicin plus cisplatin plus 5-FU (ECF). Although the response rates of these schedules are encouraging, the toxicity is considerable. Randomized trials comparing chemotherapy with best supportive care showed an increase in overall survival and in quality-of-life. Up to now adjuvant chemotherapy in curatively resected gastric cancer patients has failed to improve survival as compared with surgical controls. Phase II trials with preoperative chemotherapy have shown very promising results, but results of randomized trials should be awaited to judge the real value of this approach. At this moment it cannot yet be estimated whether preoperative chemotherapy does positively influence the resection rate and survival of patients with clinically resectable tumors.

Antineoplastic Agents↗
PubMed1997

A phase II trial of paclitaxel and weekly 24 h infusion of 5-fluorouracil/folinic acid in patients with advanced gastric cancer.

A phase II trial was performed to evaluate the efficacy and toxicity of the combination of paclitaxel and 5-fluorouracil (5-FU)/folinic acid in patients with advanced gastric carcinoma. Twenty-two patients (six female and 16 male) with advanced or metastatic disease were enrolled. None of them had received prior chemotherapy. Paclitaxel was administrated as a 3 h infusion of 175 mg/m2 at days 1 and 22, 5-FU 2000 mg/m2 i.v. over 24 h and folinic acid 500 mg/m2 i.v. 2 h prior to 5-FU weekly from days 1 to 36. Seven patients (32%) had partial remissions including the lungs, skin, lymph nodes and locally advanced primary tumor. The median overall survival was 11 months (range 1-17+) and the median progression-free interval was 8 months (range 1-13+). Neutropenia (WHO grade III/IV) occurred in 14% of patients. Other main toxicities were alopecia in 45%, fever/infection in 9%, and nausea/vomiting and diarrhea in 5%. In conclusion, the combination of paclitaxel and continuously infused 5-FU/folinic acid appears to be an active regimen for advanced gastric carcinoma with a remission rate comparable to ELF or FAMtx. The moderate toxicity allows treatment on an outpatient basis.

Adult↗
PubMed1999

Mitomycin C continuous infusion as salvage chemotherapy in pretreated patients with advanced gastric cancer.

UNLABELLED: Our purpose was to evaluate the safety and therapeutic activity of continuously infused mitomycin C in patients with recurring or progressive metastatic gastric cancer following first-line chemotherapy. Patients were treated with mitomycin C 20 mg/m2 i.v. over a time period of 120 h followed by a 3-week rest period. All patients received prednisone 50 mg p.o. prophylactically for 5 days to prevent hemolytic uremic syndrome and pulmonary side effects. Twenty-two consecutively enrolled patients were assessable for toxicity and 20 for response evaluation completing at least one full course of chemotherapy (two patients evaluable but not measurable). PATIENT CHARACTERISTICS: median age: 63 years (39-76); Sex (M/ F): 13/9; median Karnofsky status: 70% (50-100%); resection of primary tumor n = 12 (55%); sites of metastases: liver n = 17 (77%), locally advanced n = 10 (45%), peritoneum n = 13 (59%), lungs n=5 (23%), bone n=3 (14%) and lymph nodes n=14 (64%). Previous chemotherapy regimens: bolus 5-FU/folinic acid n=6 (27%), ELF n=4 (18%), EAP n=3 (14%) and continuous 5-FU/folinic acid/cisplatin/paclitaxel n=9 (41%). In 20 evaluable patients one complete and five partial remissions were observed; overall response rate 30.0% [95% confidence interval (CI): 9.1-50.9%] with a median response duration of 2.1 months (range: 2-6). The median survival was 3.6 months (95% CI: 2.1-6.0) resulting in a 6-month survival rate of 30% since start of mitomycin C. WHO grade III/IV mucositis, diarrhea and fever/infection occurred in 9% of patients each. Cumulative thrombo- and leukocytopenia (WHO grade II/IV) were observed in four and two patients, respectively. Treatment had to be stopped early in two patients. No severe renal dysfunction, pulmonary toxicity or evidence of hemolytic uremic syndrome was observed. Fatigue during the 120 h infusion of mitomycin C was common (11 of 22 patients). We conclude that continuous infusion of mitomycin C is feasible on an outpatient basis, revealing an acceptable toxicity. Mitomycin C demonstrates single-agent activity in pretreated gastric cancer, but has only limited efficacy following cisplatin/paclitaxel-based first-line chemotherapy.

Adult↗