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Cloning and characterization of the Escherichia coli K-12 rfa-2 (rfaC) gene, a gene required for lipopolysaccharide inner core synthesis.

Chen, L; Coleman, W G
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /05/1993 EN
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A genetically defined mutation, designated rfa-2, results in altered lipopolysaccharide (LPS) biosynthesis. rfa-2 mutants produce a core-defective LPS that contains lipid A and a single sugar moiety, 2-keto-3-deoxyoctulosonic acid, in the LPS core region. Such LPS core-defective or deep-rough (R) mutant structures were previously designated chemotype Re. Phenotypically, rfa-2 mutants exhibit increased permeability to a number of hydrophilic and hydrophobic agents. By restriction analyses and complementation studies, we clearly defined the rfa-2 gene on a 1,056-bp AluI-DraI fragment. The rfa-2 gene and the flanking rfa locus regions were completely sequenced. Additionally, the location of the rfa-2 gene on the physical map of the Escherichia coli chromosome was determined. The rfa-2 gene encodes a 36,000-dalton polypeptide in an in vivo expression system. N-terminal analysis of the purified rfa-2 gene product confirmed the first 24 amino acid residues as deduced from the nucleotide sequence of the rfa-2 gene coding region. By interspecies complementation, a Salmonella typhimurium rfaC mutant (LPS chemotype Re) is transformed with the E. coli rfa-2+ gene, and the transformant is characterized by wild-type sensitivity to novobiocin (i.e....

Genetic analysis of lipopolysaccharide core biosynthesis by Escherichia coli K-12: insertion mutagenesis of the rfa locus.

Austin, E A; Graves, J F; Hite, L A; Parker, C T; Schnaitman, C A
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /09/1990 EN
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Tn10 insertions were selected on the basis of resistance to the lipopolysaccharide (LPS)-specific bacteriophage U3. The majority of these were located in a 2-kilobase region within the rfa locus, a gene cluster of about 18 kb that contains genes for LPS core biosynthesis. The rfa::Tn10 insertions all exhibited a deep rough phenotype that included hypersensitivity to hydrophobic antibiotics, a reduction in major outer membrane proteins, and production of truncated LPS. These mutations were complemented by a Clarke-Carbon plasmid known to complement rfa mutations of Salmonella typhimurium, and analysis of the insert from this plasmid showed that it contained genes for at least six polypeptides which appear to be arranged in the form of a complex operon. Defects in two of these genes were specifically implicated as the cause of the deep rough phenotype. One of these appeared to be rfaG, which encodes a function required for attachment of the first glucose residue to the heptose region of the core. The other gene did not appear to be directly involved in determination of the sugar composition of the core. We speculate that the product of this gene is involved in the attachment of phosphate or phosphorylethanolamine to the core and that it is the lack of one of these substituents which results in the deep rough phenotype.

New cysE-pyrE-linked rfa mutation in Escherichia coli K-12 that results in a heptoseless lipopolysaccharide.

Coleman, W G; Deshpande, K S
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /03/1985 EN
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A new novobiocin-supersensitive mutant of Escherichia coli K-12 has been characterized biochemically and genetically. Lipopolysaccharide prepared from this mutant strain is truncated and contains 2-keto-3-deoxyoctulosonic acid as its only core sugar. This new core-defective mutation, designated rfa-2, results in increased sensitivity to several hydrophobic and some hydrophilic agents. Genetic analysis of the rfa mutant indicated that the rfa-2 locus is located at 81 min on the chromosome. The order of the genes in this region based on transduction analysis is xyl cysE rfa-2 rfaD70 pyrE. P1 transduction analyses indicate that the rfa-2 marker is nonallelic with the recently described cysE-pyrE-linked rfaD70 locus. Plasmids carrying the wild-type rfaD70+ allele failed to abolish the rfa-2 phenotypes. Further, the rfaD gene product, ADP-L-glycero-D-mannoheptose-6-epimerase, was detected in crude extracts of a rfa-2 mutant strain, CL609, and was absent in the rfaD70 mutant. The wild-type rfa-2 allele codes either for a specific heptose biosynthetic enzyme (different from the rfaD gene product) or an enzymatic activity required for the addition of heptose to the lipid A-2-keto-3-deoxyoctulosonic acid acceptor.

Mapping of rfa Genes in Salmonella typhimurium by ES18 and P22 Transduction and by Conjugation

Kuo, Tseng-Tong; Stocker, B. A. D.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1972 EN
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Loci termed rfa, determining biosynthesis of somatic lipopolysaccharide core, have been mapped in Salmonella typhimurium LT2. The smooth-specific phage P22 co-transduced two leaky rfa alleles with cysE and with pyrE; one of the leaky alleles is perhaps rfaG, and the other is an unidentified gene concerned with synthesis of the heptose-containing part of the core. The lipopolysaccharide-indifferent phage ES18 (or its variant ES18.h1) co-transduced rfaF, rfaG, rfaL, rfa(R-res-1), and rfa(R-res-2) alleles with cysE and with pyrE, at rates indicating the order cysE–rfaF–(rfa[R-res-1], rfa[r-res-2], rfaL)–rfaG–pyrE. One proven (and two suspected) rfaE alleles and five proven rfaH alleles were not co-transduced with cysE or pyrE. Hfr crosses indicated that the proven rfaE allele mapped between serA and strA.

P22-Mediated Transduction Analysis of the Rough A (rfa) Region of the Chromosome of Salmonella typhimurium

Sanderson, Kenneth E.; Saeed, Yousuf A.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1972 EN
Relevância na Pesquisa
27.39%
Seven temperature-sensitive rough mutants of Salmonella typhimurium were found to be sensitive to smooth-specific phages at low temperature (25 C, 30 C) and resistant or partially resistant to rough-specific phages, whereas at high temperatures (37 C, 45 C) they were resistant or partially resistant to smooth-specific phages but sensitive to rough-specific phages. These data indicate that at low temperature each strain makes lipopolysaccharide which is relatively normal, but at high temperatures O-specific side chains are not added to the lipopolysaccharide. At 45 C, these strains have the R-res-1 or R-res-2 phage sensitivity phenotype, and their genetic lesions map by P22-mediated transduction in the rfa gene cluster between cysE-pyrE, suggesting a mutation in genes with transferase functions. P22-mediated joint transduction with temperature-sensitive rfa mutants, leaky rfa mutants, and rfa P22 lysogens have shown the following order of genes in the S. typhimurium linkage map: xyl-mtlA-mtlB-cysE-rfaF-rfaG-pyrE. An rfaE allele was not jointly transduced in the cysE-pyrE segment.

Insertion of the F Factor into the Cluster of rfa (Rough A) Genes of Salmonella typhimurium

Sanderson, Kenneth E.; Saeed, Hamida
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/1972 EN
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27.47%
From F+ strains of Salmonella typhimurium, isolates were obtained representing two new classes of Hfr strains, HfrK1 and HfrK2, in which the insertion of the F factor into the rfa genes results in chromosome mobilization either clockwise or anticlockwise from rfa, and in the Rfa phenotype. The point of insertion of the F factor into the cluster of rfa genes, revealed by studies of the early transfer of their normal alleles, is as follows: xyl-cysE-rfa-657 (HfrK2-1, SA540 →)–(← HfrK1-1, SA458)–rfaG-(← HfrK1-2, SA464)–pyrE-metA

Role of the rfa locus in the immunogenicity of common enterobacterial antigen.

Marx, A; Petcovici, M
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /02/1976 EN
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Escherichia coli O14 is one of the few strains of Enterobacteriaceae which in the rabbit engender antibodies in high titers against the common enterobacterial antigen (CA). It is a rough strain that does not possess a specific side chain in its lipopolysaccharide structure (rfa+rfb-). An rfa mutant (rfa-rfb-) was isolated from this parental strain. Chemical analysis revealed the absence of one glucose and of one galactose molecule in the core polysaccharide of the mutant. The incomplete synthesis of the core was accompanied by loss of immunogenicity of CA. In the mutant, in contrast to the wild type, CA was not bound to the core; hence, the core lipopolysaccharide might exert immunosuppressive activity on CA. A protein fraction of normal rabbit serum was shown to destroy the erythrocyte-coating capacity of CA. This fraction also displayed immunosuppressive activity on free CA but not on CA bound to the core polysaccharide.

An experimental study of the treatment of liver injury with InLine RFA

Yao, Peng; Gunasegaram, Aravin; Ladd, Leigh A.; Daniel, Steven; Morris, David L.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em //2007 EN
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Background: The liver is the most frequently injured abdominal organ after blunt injury; sometimes it may be very difficult to achieve haemostasis. In this study we examined the use of InLine radiofrequency ablation (RFA) for the coagulation and haemostasis of simulated liver injury. Materials and methods: Six pigs were tested in this study. We created two types of grade III to IV liver injury: peripheral and central. Then treatment with InLine RFA was compared to conventional diathermy and suture. A total of 32 surgeries were performed: peripheral injury (12 InLine versus 6 diathermy + suture); central injury (8 InLine versus 6 diathermy + suture). Results: The reduction of blood loss was 63.88% in peripheral injury and 53.57% in central injury, respectively. There were significant differences in both types of injuries as regards blood loss (p<0.05) and blood loss per cm2 (p <0.05). Conclusions: InLine RFA is efficacious in treating liver injuries in pigs and may have a significant potential for some human liver injuries.

The sonographer’s role in RFA therapy of liver lesions

Mandarano, S; Mandarano, G; Sim, JH
Fonte: Department of Biomedical Imaging, Faculty of Medicine, University of Malaya, Malaysia Publicador: Department of Biomedical Imaging, Faculty of Medicine, University of Malaya, Malaysia
Tipo: Artigo de Revista Científica
Publicado em 01/01/2009 EN
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27.28%
Interventional techniques using ultrasound guidance, such as Radio Frequency Ablation (RFA) of liver lesions, are the domain of the radiologist. However, real time ultrasound imaging as performed by the sonographer, is critical in monitoring the successful insertion and placement of the RFA needle. RFA is used to create a localised and controlled application of heat in order to induce necrosis of cells within the liver lesions.

Endoscopic Ultrasound-Guided Radiofrequency Ablation (EUS-RFA) of the Pancreas in a Porcine Model

Gaidhane, Monica; Smith, Ioana; Ellen, Kristi; Gatesman, Jeremy; Habib, Nagy; Foley, Patricia; Moskaluk, Christopher; Kahaleh, Michel
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
EN
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27.39%
Backgrounds. Limited effective palliative treatments exist for pancreatic cancer which includes surgery or chemotherapy. Radiofrequency ablation (RFA) uses high frequency alternating current to ablate diseased tissue and has been used to treat various tumors. In this study, we evaluated a prototype probe adjusted to the EUS-needle to perform EUS-RFA to permit coagulative necrosis in the pancreas. Methods. Five Yucatan pigs underwent EUS-guided radiofrequency ablation of the head of their pancreas. Using an EUS-needle, RFA was applied with 6 mm and then 10 mm of the probe exposed at specific wattage for preset durations. Results. Only one pig showed moderate levels of pancreatitis (20% proximal pancreatitis). The other animals showed much lower areas of tissue damage. In 3 of the 5 pigs, the proximal pancreas showed greater levels of tissue injury than the distal pancreas, consistent with the proximity of the tissue to the procedure site. In 1 pig, both proximal and distal pancreas showed minimal pancreatitis (1%). There was minimal evidence of fat necrosis in intra-pancreatic and/or extra-pancreatic adipose tissue. Conclusion. EUS-guided RFA of the pancreatic head with the monopolar probe through a 19-gauge needle was well tolerated in 5 Yucatan pigs and with minimal amount of pancreatitis.

Electromagnetic Tracking Navigation to Guide Radiofrequency Ablation (RFA) of a Lung Tumor

Amalou, Hayet; Wood, Bradford J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/2012 EN
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27.28%
Radiofrequency ablation (RFA) may be an option for patients with lung tumors who have unresectable disease and are not suitable for available palliative modalities. RFA electrode positioning may take several attempts, necessitating multiple imaging acquisitions or continuous use of CT (Computed Tomography). Electromagnetic tracking utilizes miniature sensors integrated with RFA equipment to guide tools in real-time, while referencing to pre-procedure imaging. This technology was demonstrated successfully during a lung tumor ablation, and was more accurate at targeting the tumor, compared to traditional freehand needle insertion. It is possible, although speculative and anecdotal, that more accuracy could prevent unnecessary repositioning punctures and decrease radiation exposure. Electromagnetic tracking has theoretical potential to benefit minimally invasive interventions.

Surveillance of HCC Patients after Liver RFA: Role of MRI with Hepatospecific Contrast versus Three-Phase CT Scan—Experience of High Volume Oncologic Institute

Granata, Vincenza; Petrillo, Mario; Fusco, Roberta; Setola, Sergio Venanzio; de Lutio di Castelguidone, Elisabetta; Catalano, Orlando; Piccirillo, Mauro; Albino, Vittorio; Izzo, Francesco; Petrillo, Antonella
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.28%
Purpose. To compare the diagnostic accuracy of hepatospecific contrast-enhanced MRI versus triple-phase CT scan after radiofrequency ablation (RFA) in hepatocellular carcinoma (HCC) patients. Methods. Thirty-four consecutive HCC patients (42 hepatic nodules) were treated with percutaneous RFA and underwent MR and CT scans. All patients were enrolled in a research protocol that included CT with iodized contrast medium injection and MR with hepatospecific contrast medium injection. All patients were restaged within four weeks and at 3 months from ablation. The images were reviewed by four different radiologists to evaluate tumor necrosis, residual or recurrence disease, and evidence of new foci. Results. Thirty-two nodules were necrotic after treatment; 10 showed residual disease. Six new HCCs were identified. At first month followup CT has identified 34 necrotic lesions and 8 residual diseases; no new foci were recognized. At MRI instead, 32 complete necrotic lesions were identified, 10 lesions showed residual disease, and 2 new HCCs were found. At three months, CT demonstrated 33 completely necrotic lesions, 9 residual diseases, and 2 new HCCs. MR showed 31 complete necrotic lesions, 11 cases of residual disease, and 6 new HCCs. Conclusions. Hepatospecific contrast-enhanced MRI is more effective than multiphase CT in assessment of HCC treated with RFA.

Therapeutic response assessment of RFA for HCC: Contrast-enhanced US, CT and MRI

Minami, Yasunori; Nishida, Naoshi; Kudo, Masatoshi
Fonte: Baishideng Publishing Group Co., Limited Publicador: Baishideng Publishing Group Co., Limited
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.62%
Radiofrequency ablation (RFA) is commonly applied for the treatment of hepatocellular carcinoma (HCC) because of the facile procedure, and the safety and effectiveness for the treatment of this type of tumor. On the other hand, it is believed that HCC cells should spread predominantly through the blood flow of the portal vein, which could lead to the formation of intrahepatic micrometastases. Therefore, monitoring tumor response after the treatment is quite important and accurate assessment of treatment response is critical to obtain the most favorable outcome after the RFA. Indeed, several reports suggested that even small HCCs of ≤ 3 cm in diameter might carry intrahepatic micrometastases and/or microvascular invasion. From this point of view, for preventing local recurrences, RFA should be performed ablating a main tumor as well as its surrounding non-tumorous liver tissue where micrometastases and microvascular invasion might exist. Recent advancement of imaging modalities such as contrast-enhanced ultrasonic, computed tomography, and magnetic resonance imaging are playing an important role on assessing the therapeutic effects of RFA. The local recurrence rate tends to be low in HCC patients who were proven to have adequate ablation margin after RFA; namely...

The future of radiofrequency ablation is looking BETA : short and long term studies of bimodal electric tissue ablation (BETA) in a porcine model.

Dobbins, Christopher
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2008
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27.39%
Introduction: Radiofrequency ablation (RFA) is a popular method of treating unresectable liver tumours by the use of a high frequency, alternating electrical current that heats and destroys tumour cells. The size of the ablation is limited by localised charring of adjacent tissue that prevents further conduction of the radiofrequency current. In the clinical setting, this results in increased rates of local recurrence in tumours that are greater than 3 cm in diameter as multiple, overlapping ablations need to be performed to treat the one tumour. To overcome this problem, a modified form of RFA called Bimodal Electric Tissue Ablation (BETA) has been created. BETA adds a direct electrical current to the alternating radiofrequency current, thus establishing its bimodal character. When direct currents are used in biological tissues, water is transferred from anode to cathode by a process called electro-osmosis. By attaching the cathode to the radiofrequency electrode, water is attracted to the area thus preventing tissue desiccation and charring. The BETA circuit has been constructed and tested using a porcine model. The aims of the studies are to confirm that larger ablations can be produced with the BETA system and that it is safe to use in an animal model. Three studies have been performed to test these aims in porcine liver. Methods: The first study was designed to compare sizes of the ablation produced between standard RFA and the BETA circuit. This was followed by a long-term study to assess associated changes to liver function and pathological changes within the liver as well as identifying any other treatment related morbidity. The third study assessed the difference in ablation size and safety aspects when the positive electrode of the direct current circuitry was moved from small surface area under the skin to a large surface area on the skin. Results: Ablations with significantly larger diameters are created with the BETA circuit using a multi-tine needle (49.55 mm versus 27.78 mm...

Bimodal electric tissue ablation-modified radiofrequency ablation with a Le Veen electrode in a pig model

Dobbins, C.; Wemyss-Holden, S.; Cockburn, J.; Maddern, G.
Fonte: Academic Press Inc Elsevier Science Publicador: Academic Press Inc Elsevier Science
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
Relevância na Pesquisa
27.28%
Radiofrequency ablation (RFA) is a method of treating non-resectable liver tumors by use of a high-frequency alternating electrical current. Concerns have been raised as the local recurrence rates following treatment have been reported to be as high as 47%. The size of the ablation is limited by charring of adjacent tissues. It is hypothesized that by hydrating the liver, we can reduce charring, thus producing larger ablations, and that this can be achieved by addition of a direct electrical current to the electrical circuit. Using a pig model, standard RFA control ablations were created in the left lobe of the liver. Ablations using the modified circuit were created in the right lobe. At the end of the procedure, the pig was killed by lethal injection and the liver harvested. From the explanted liver, the diameter of each ablation was measured and the modified ablations were compared with controls using restricted maximum likelihood variance analysis. From 4 pigs, 14 controls and 12 modified ablations were produced. The mean diameter of the controls was 27.78 mm (± SE 3.37 mm). The mean diameter of the modified ablation was 49.55 mm (± SE 3.46 mm), which was significantly larger than the controls (P < 0.001). This study has shown that by modification of the standard RFA circuit with the addition of a direct electrical current...

Bimodal electric tissue ablation (BETA) - Effect of reversing the polarity of the direct current on the size of ablation

Tiong, L.; Finnie, J.; Field, J.; Maddern, G.
Fonte: Academic Press Inc Elsevier Science Publicador: Academic Press Inc Elsevier Science
Tipo: Artigo de Revista Científica
Publicado em //2012 EN
Relevância na Pesquisa
27.28%
BACKGROUND: Bimodal electric tissue ablation (BETA) is a new technique that uses the direct current in electrolysis to improve the efficacy of radio frequency (RF) ablation. It was hypothesized that attaching the cathode of the electrolytic circuit to the RF electrode will increase the tissue hydration, therefore delaying tissue desiccation during ablation. Consequently, the ablation process can continue for a longer period of time and produce larger ablations. This hypothesis was tested by reversing the polarity of the electrolytic circuit, which theoretically would cause tissue desiccation and therefore produce smaller ablations. This new setup is called reversed polarity bimodal electric ablation (RP-BEA). MATERIALS AND METHODS: Three types of ablations standard radiofrequency ablation (RFA), BETA, and RP-BEA) were tested in a pig liver model. In BETA and RP-BEA, 9 V of direct current were provided for 10 min, after which the rf generator were switched on and both electrical circuits allowed to run concurrently. In all three setups, ablations were continued until "roll-off." The size of ablation was measured and compared with each other. RESULTS: The duration of ablation was significantly shorted in RP-BEA compared with standard RFA and BETA (48 s verus 148 s and 84 s...

Bimodal electric tissue ablation (BETA) compared with the Cool-Tip RFA system

Tiong, L.; Field, J.; Maddern, G.
Fonte: Blackwell Science Asia Publicador: Blackwell Science Asia
Tipo: Artigo de Revista Científica
Publicado em //2012 EN
Relevância na Pesquisa
27.7%
Background:  Bimodal electric tissue ablation (BETA) incorporates the process of electrolysis into radiofrequency ablation (RFA) to increase the size of tissue ablation. This study investigated whether BETA could increase the efficacy of the Cool-Tip RF system (Covidien, Boulder, CO, USA) to produce larger ablations. It also investigated whether applying electrolysis only during the pretreatment phase (called electrochemical treatment (ECT)/RFA group) is as effective as BETA (where electrolysis was used during both the pretreatment and RFA phases). Methods:  A Cool-Tip RF system (Covidien) was used to test three types of ablations (RFA, BETA, and ECT/RFA) in a pig liver model. In BETA, 9 V of direct current was provided for 10 min, after which the RF generator was started and both electrical circuits were allowed to run concurrently. In ECT/RFA, however, the direct current circuit was switched off after 10 min of pretreatment and only RFA was performed as described above. Ablation sizes were measured in three dimensions. Results:  The size of ablations (transverse diameter A and B) produced by BETA and ECT/RFA was significantly larger compared with standard RFA (P < 0/001). BETA also created larger ablations compared with ECT/RFA (P < 0.001). Conclusion:  BETA could improve the efficacy of the Cool-Tip RF system (Covidien) to achieve larger ablations. The increased tissue hydration improved delivery of electrical energy to the tissues and delayed the process of desiccation...

Bimodal Electric Tissue Ablation (BETA): A study on ablation size when the anode is placed on the peritoneum and the liver

Tiong, L.; Finnie, J.; Field, J.; Maddern, G.
Fonte: Academic Press Inc Elsevier Science Publicador: Academic Press Inc Elsevier Science
Tipo: Artigo de Revista Científica
Publicado em //2012 EN
Relevância na Pesquisa
27.47%
BACKGROUND: In bimodal electric tissue ablation (BETA), the cathode of the DC circuit is attached to the radiofrequency (RF) electrode to increase the surrounding tissue hydration. This will delay tissue desiccation and allowing the ablation process to continue for a longer period of time before "roll-off" occurs, resulting in larger ablations compared with standard radiofrequency ablation (RFA). Previous research showed that attaching the anode to the skin using electrosurgical grounding pads would reduce the efficacy of BETA because of the high electrical resistivity of the skin. This study investigated the ablation size produced when the anode was attached to the peritoneum (BETA-peritoneum) and the liver (BETA-liver) respectively. MATERIALS AND METHODS: The anode of the DC circuit in BETA was attached to the peritoneum and the liver in a pig model using ECG dots. In BETA, 9 V of DC was provided for 10 min, after which the radiofrequency generator were switched on and both electrical circuits allowed to run concurrently until "roll-off." The size of ablations produced was compared to when the anode attached to the skin (BETA-skin) and standard RFA, respectively. The sites of anode placement were examined for local tissue injury. RESULTS: The transverse diameters in BETA-peritoneum and BETA-liver were significantly larger compared with BETA-skin and standard RFA...

Klinische Effektivität der perkutanen Radiofrequenzablation bei Patienten mit kolorektalen Lebermetastasen; Clinical efficacy of percutaneous radiofrequency ablation in patients with colorectal liver metastases

Fischer, Stefan Thomas
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
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27.86%
Nach Schätzungen erkranken weltweit jährlich circa eine Millionen Menschen an kolorektalen Karzinomen und in Deutschland sind sie die zweithäufigste Todesursache bei Tumorerkrankungen mit fast 50.000 Todesfällen jährlich. Da bis zu 60% der Patienten im Verlaufe ihrer Erkrankung Lebermetastasen entwickeln ist die Behandlung zu einem wichtigen, interdisziplinären Behandlungsfokus geworden. Als kurativer Ansatz ist die Lebermetastasenchirurgie etabliert, durch sie überleben ungefähr 40% der Patienten 5 Jahre und ungefähr 25% 10 Jahre. Dennoch ist nur für 15-20% aller Patienten mit kolorektalen Lebermetastasen für eine primäre Leberoperation möglich. Durch moderne Chemotherapie werden bis 34% der Patienten sekundär resektabel. Ist nach Chemotherapie keine Operation möglich, können die Patienten entweder palliativ chemotherapiert oder lokal abladiert werden. Die RFA ist das verbreitetste thermoablative Verfahren, mit geringer Komplikations- und hoher Erfolgsrate. In bisherigen Studien über die perkutane RFA von kolorektalen Lebermetastasen sind 5-Jahresüberlebensraten von 17-33% und ein medianes Gesamtüberleben von 31,5-36 Monaten beschrieben. In dieser retrospektiven Studie sind 238 Patienten aus drei Zentren für interventionelle Radiologie zusammengefasst. Untersucht sind das Gesamtüberleben...

An Ex Vivo Model in Human Femoral Heads for Histopathological Study and Resonance Frequency Analysis of Dental Implant Primary Stability

Hern??ndez-Cort??s, Pedro; Monje, Alberto; Galindo-Moreno, Pablo; Catena Mart??nez, Andr??s; Ortega-Oller, Inmaculada; Salas-P??rez, Jos??; Mesa, Francisco; G??mez-S??nchez, Rafael; Aguilar Pe??a, Mariano; Aguilar Pe??a, David; O'Valle, Francisco
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
27.28%
Objective. This study was designed to explore relationships of resonance frequency analysis (RFA)???assessed implant stability (ISQ values) with bone morphometric parameters and bone quality in an ex vivo model of dental implants placed in human femoral heads and to evaluate the usefulness of this model for dental implant studies. Material and Methods. This ex vivo study included femoral heads from 17 patients undergoing surgery for femoral neck fracture due to osteoporosis (OP) ( ) or for total prosthesis joint replacement due to severe hip osteoarthrosis (OA) ( ). Sixty ???mm Dentsply Astra implants were placed, followed by RFA. CD44 immunohistochemical analysis for osteocytes was also carried out. Results. As expected, the analysis yielded significant effects of femoral head type (OA versus OA) ( ), but not of the implants ( ) or of the interaction of the two factors ( ). Bonferroni post hoc comparisons showed a lower mean ISQ for implants in decalcified ( ) heads than in fresh ( ) or fixated ( ) heads (both ). The ISQ score (fresh) was significantly higher for those in OA ( ) versus OP ( ) heads. However, mixed linear analysis showed no significant association between ISQ scores and morphologic or histomorphometric results ( in all cases)...