Biomedical subjects

Y Ni

Publications and source records attributed to Y Ni.

At least 19 recordsLinked to original sources

PubMed2006

Control of electron localization in molecular dissociation.

We demonstrated how the subcycle evolution of the electric field of light can be used to control the motion of bound electrons. Results are presented for the dissociative ionization of deuterium molecules (D2 --> D+ + D), where asymmetric ejection of the ionic fragment reveals that light-driven intramolecular electronic motion before dissociation localizes the electron on one of the two D+ ions in a controlled way. The results extend subfemtosecond electron control to molecules and provide evidence of its usefulness in controlling reaction dynamics.

Journal Article↗

PubMed2006

Vesicular glutamate transporter expression in supraoptic neurones suggests a glutamatergic phenotype.

Magnocellular neuroendocrine cells of the supraoptic nucleus (SON) release the peptides oxytocin (OT) and vasopressin (VP) from their dendrites and terminals. In addition to peptide-containing large dense-core vesicles, axon terminals from these cells contain clear microvesicles that have been shown to contain glutamate. Using multilabelling confocal microscopy, we investigated the presence of vesicular glutamate transporters (VGLUTs) in astrocytes as well as VP and OT neurones of the SON. Simultaneous probing of the SON with antibodies against VGLUT isoforms 1-3, OT, VP and glial fibrillary acidic protein (GFAP) revealed the presence of VGLUT-2 in somata and dendrites of SON neurones. Immunoreactivity (-ir) for VGLUT-3 was also detected in both OT and VP neurones as well as in GFAP-ir astrocytes and other cells of the ventral glial lamina. Colocalisation of VGLUT-2 and VGLUT-3 in individual SON neurones was also examined and VGLUT-ir with both antibodies could be detected in both types of SON neurones. Although VGLUT-1-ir was strong lateral to the SON, only sparse labelling was apparent within the nucleus, and no colocalisation with either SON neurones or astrocytes was observed. The SON or the SON plus its surrounding perinuclear zone was probed using the reverse transcriptase-polymerase chain reaction and the presence of mRNA for all three VGLUT isoforms was detected. These results suggest that similar arrangements of transmitters exist in SON neuronal dendrites and their neurohypophysial terminals and that magnocellular neuroendocrine somata and dendrites may be capable of glutamatergic transmission.

Animals↗

PubMed2005

Response of polyatomic molecules to ultrastrong laser- and ion-induced fields.

The exposure of molecules to short, ultrastrong electric fields leads to multiple ionization and a subsequent Coulomb explosion. We present a comparative study where uracil molecules are exposed to fields generated by high-power laser pulses (tau approximately 75 fs, I > 10(16) W/cm2) or swift highly charged ions (0.5 MeV Xe25+) representing a half-cycle pulse of less than 10 fs duration. Molecular dynamics and structural information contained in the fragmentation pathways can be assessed separately. Despite the similar field strengths large differences in fragment kinetic energies are found which are related to field shape and duration with the aid of molecular dynamics simulations.

Journal Article↗

PubMed2005

Estimation of the cortical functional connectivity with the multimodal integration of high-resolution EEG and fMRI data by directed transfer function.

Nowadays, several types of brain imaging device are available to provide images of the functional activity of the cerebral cortex based on hemodynamic, metabolic, or electromagnetic measurements. However, static images of brain regions activated during particular tasks do not convey the information of how these regions communicate with each other. In this study, advanced methods for the estimation of cortical connectivity from combined high-resolution electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) data are presented. These methods include a subject's multicompartment head model (scalp, skull, dura mater, cortex) constructed from individual magnetic resonance images, multidipole source model, and regularized linear inverse source estimates of cortical current density. Determination of the priors in the resolution of the linear inverse problem was performed with the use of information from the hemodynamic responses of the cortical areas as revealed by block-designed (strength of activated voxels) fMRI. We estimate functional cortical connectivity by computing the directed transfer function (DTF) on the estimated cortical current density waveforms in regions of interest (ROIs) on the modeled cortical mantle. The proposed method was able to unveil the direction of the information flow between the cortical regions of interest, as it is directional in nature. Furthermore, this method allows to detect changes in the time course of information flow between cortical regions in different frequency bands. The reliability of these techniques was further demonstrated by elaboration of high-resolution EEG and fMRI signals collected during visually triggered finger movements in four healthy subjects. Connectivity patterns estimated for this task reveal an involvement of right parietal and bilateral premotor and prefrontal cortical areas. This cortical region involvement resembles that revealed in previous studies where visually triggered finger movements were analyzed with the use of separate EEG or fMRI measurements.

Adult↗

PubMed2005

Progesterone primes zona pellucida-induced activation of phospholipase A2 during acrosomal exocytosis in guinea pig spermatozoa.

We investigated, using guinea-pig spermatozoa as a model, whether phospholipase A2 (PLA2) is involved in progesterone or zona pellucida (ZP)-stimulated acrosomal exocytosis, if progesterone enhances ZP-induced activation of PLA2, and mechanisms underlying PLA2 regulation. Spermatozoa were capacitated and labeled in low Ca2+ medium with [14C]choline chloride or [14C]arachidonic acid, washed, and then exposed to millimolar Ca2+ and progesterone and/or ZP. Each agonist stimulated decrease of phosphatidylcholine (PC) and release of arachidonic acid and lysoPC, indicative of PLA2 activation. Aristolochic acid (a PLA2 inhibitor) abrogated lipid changes and exocytosis, indicating that these lipid changes are essential for exocytosis. Exposure of spermatozoa to submaximal concentrations of both progesterone and ZP resulted in a synergistic increase of arachidonic acid and lysoPC releases, and exocytosis, suggesting that, under natural conditions, both agonists interact to bring about acrosomal exocytosis. Progesterone-induced PLA2 activation appears to be mediated by a GABA(A)-like receptor, because bicuculline (a GABA(A) receptor antagonist) blocked arachidonic acid release and exocytosis. In agreement with this, GABA mimicked progesterone actions. ZP-induced activation of PLA2 seemed to be transduced via G(i) proteins because pertussis toxin blocked arachidonic acid release and acrosomal exocytosis. PLA2 may be regulated by PKC because progesterone- or ZP-induced release of arachidonic acid was blocked by the PKC inhibitors staurosporine or chelerythrine chloride. PLA2 could also be regulated by the cAMP-PKA pathway; inclusion of the PKA inhibitor 14-22 amide or H-89 led to a reduction in arachidonic acid release or exocytosis after progesterone or ZP. Taken together, these results suggest that PLA2 plays an essential role in progesterone or ZP-stimulated exocytosis with progesterone priming ZP action.

Acrosome↗

PubMed2004

Assessing cortical functional connectivity by linear inverse estimation and directed transfer function: simulations and application to real data.

OBJECTIVE: To test a technique called Directed Transfer Function (DTF) for the estimation of human cortical connectivity, by means of simulation study and human study, using high resolution EEG recordings related to finger movements. METHODS: The method of the Directed Transfer Function (DTF) is a frequency-domain approach, based on a multivariate autoregressive modeling of time series and on the concept of Granger causality. Since the spreading of the potential from the cortex to the sensors makes it difficult to infer the relation between the spatial patterns on the sensor space and those on the cortical sites, we propose the use of the DTF method on cortical signals estimated from high resolution EEG recordings, which exhibit a higher spatial resolution than conventional cerebral electromagnetic measures. The simulation study was followed by an analysis of variance (ANOVA) of the results obtained for different levels of Signal to Noise Ratio (SNR) and temporal length, as they have been systematically imposed on simulated signals. The whole methodology was then applied to high resolution EEG data recorded during a visually paced finger movement. RESULTS: The statistical analysis performed returns that during simulations, DTF is able to estimate correctly the imposed connectivity patterns under reasonable operative conditions, i.e. when data exhibit a SNR of at least 3 and a length of at least 75 s of non-consecutive recordings at 64 Hz of sampling rate, equivalent, more generally, to 4800 data samples. CONCLUSIONS: Functional connectivity patterns of cortical activity can be effectively estimated under general conditions met in any practical EEG recordings, by combining high resolution EEG techniques, linear inverse estimation and the DTF method. SIGNIFICANCE: The estimation of cortical connectivity can be performed not only with hemodynamic measurements, by using functional MRI recordings, but also with modern EEG recordings treated with advanced computational techniques.

Analysis of Variance↗

PubMed2004

Isolation and characterization of structural components of Aloe vera L. leaf pulp.

The clear pulp, also known as inner gel, of Aloe vera L. leaf is widely used in various medical, cosmetic and nutraceutical applications. Many beneficial effects of this plant have been attributed to the polysaccharides present in the pulp. However, discrepancies exist regarding the composition of pulp polysaccharide species and an understanding of pulp structure in relation to its chemical composition has been lacking. Thus, we examined pulp structure, isolated structural components and determined their carbohydrate compositions along with analyzing a partially purified pulp-based product (Acemannan hydrogel) used to make Carrisyn hydrogel wound dressing. Light and electron microscopy showed that the pulp consisted of large clear mesophyll cells with a diameter as large as 1000 microm. These cells were composed of cell walls and cell membranes along with a very limited number of degenerated cellular organelles. No intact cellular organelles were found in mesophyll cells. Following disruption of pulp by homogenization, three components were isolated by sequential centrifugation. They were thin clear sheets, microparticles and a viscous liquid gel, which corresponded to cell wall, degenerated cellular organelles and liquid content of mesophyll cells based on morphological and chemical analysis. These three components accounted for 16.2% (+/-3.8), 0.70% (+/-0) and 83.1% of the pulp on a dry weight basis. The carbohydrate composition of each component was distinct; liquid gel contained mannan, microparticles contained galactose-rich polysaccharide(s) and cell walls contained an unusually high level of galacturonic acid (34%, w/w; Gal A). The same three components were also found in Acemannan Hydrogel with mannan as the predominant component. Thus, different pulp structural components are associated with different polysaccharides and thus may potentially be different functionally. These findings may help lay a basis for further studies and development of better controlled processing methods and applications for this well-accepted medicinal plant.

Aloe↗

PubMed2004

Control of atomic ionization by two-color few-cycle pulses.

We have studied the ionization of Rydberg atoms by few-cycle radio-frequency pulses and used two-color fields to control the ionization dynamics. We show that the number of times that electrons are emitted during a pulse can be limited and that the duration of the electron emission can be shortened. These results, once they are transposed to the optical domain, may inspire new strategies for the production of single attosecond pulses.

Journal Article↗

PubMed2003

Attosecond angle-resolved photoelectron spectroscopy.

We report experiments on the characterization of a train of attosecond pulses obtained by high-harmonic generation, using mixed-color (XUV+IR) atomic two-photon ionization and electron detection on a velocity map imaging detector. We demonstrate that the relative phase of the harmonics is encoded both in the photoelectron yield and the angular distribution as a function of XUV-IR time delay, thus making the technique suitable for the detection of single attosecond pulses. The timing of the attosecond pulse with respect to the field oscillation of the driving laser critically depends on the target gas used to generate the harmonics.

Photons↗

PubMed2003

Construction and characterization of a recombinant ovine lentivirus carrying the optimized green fluorescent protein gene at the dUTPase locus.

AdUTPase gene ( du) deleted ovine lentivirus (OvLV(Deltadu)) mutant, derived from Visna/maedi virus (VMV) molecular clone KV1772, was constructed. Subsequently, a copy of the optimized green fluorescent protein ( egfp) coding region was fused into the viral pol open reading frame (ORF) at the deleted du locus to generate viral mutant, OvLV(Deltadu-egfp). OvLV(Deltadu) reverse transcriptase (RT) activity and titer of infectious virus in goat synovial membrane (GSM) cell cultures were not affected compared to that of KV1772 and OvLV-85/34 strain (p < 0.05). By contrast, OvLV(Deltadu-egfp) RT activity and virus titer were lower than for KV1772 and OvLV(Deltadu) (p < 0.05). OvLV-85/34 RT in sheep monocyte-derived macrophages (SMDM) was higher than that of KV1772, OvLV(Deltadu) and OvLV(Deltadu-egfp) (p < 0.05). The ability to prevent dUTP mis-incorporation into newly synthesized DNA was disrupted in OvLV(Deltadu) and OvLV(Deltadu-egfp) (p < 0.05). Immunoprecipitation demonstrated that GFP is expressed by OvLV(Deltadu-egfp) at a low level. OvLV(Deltadu-egfp) retained egfp after 10 passages in cell culture.OvLV(Deltadu-egfp) was re-isolated in GSM cells from peripheral blood mononuclear (PBMN) cells of three of four OvLV(Deltadu-egfp)-inoculated lambs, but by contrast to the in vitro experiments OvLV(Deltadu-egfp) lost the insert. Priming with OvLV(Deltadu-egfp) did not prevent infection with pathogenic OvLV, but cell-associated viremia in a mock-infected contact control lamb was higher than in OvLV(Deltadu-egfp)-primed lambs. OvLV serum antibody titers increased steadily in OvLV(Deltadu-egfp)-inoculated lambs, but in a lamb from which OvLV(Deltadu-egfp) was not reisolated the antibody titer surpassed the negative/positive cut-off value only after challenge with OvLV-85/34. Because OvLV(Deltadu-egfp) is attenuated for pathogenicity in vitro, replicates in vivo and stimulates an antibody response, subsequent experiments need to address the likelihood of using OvLV(Deltadu-egfp) as an attenuated, live-virus vaccine to protect sheep against OvLV-induced disease when challenged with pathogenic OvLV.

Animals↗

PubMed2003

Size and geometry of hepatic radiofrequency lesions.

AIM: To report and compare the size and geometry of hepatic radiofrequency (RF) lesions using the currently available commercial devices. METHODS: A literature search was carried out for the period from January 1st 1990 to June 15th 2003. The commercial suppliers were asked to provide all available data. For each electrode and protocol, size and geometry of single-cycle thermal lesions were registered. RESULTS: No information at all on size and geometry of the inducible lesions was available for 17 of the 28 current commercial electrodes. Many descriptions of RF lesions are limited to the mean transverse diameter. With normal blood flow, diameter of lesions is often smaller than suggested by the length of the electrode tip or the diameter of the deployed prongs. Lesions are rarely perfect spheres but either ellipses or flattened spheres. Distortion of the RF lesion by nearby blood vessels is very common. Fusion of thermal zones between prongs of expandable electrodes can be incomplete. Blood flow interruption using a Pringle maneuver yields larger lesions that are less distorted and more complete. CONCLUSIONS: There is insufficient experimental data for many electrodes that are currently used in patients. RF companies should provide these data before releasing electrodes for use. For those electrodes for which data exist, coagulation lesions are often smaller, less spherical, less complete and less regular than generally presumed. Accurate knowledge of size and geometry of RF lesions is crucial to prevent local recurrence.

Animals↗

PubMed2002

Complications of radiofrequency coagulation of liver tumours.

BACKGROUND: Radiofrequency coagulation (RFC) is being promoted as a novel technique with a low morbidity rate in the treatment of liver tumours. The purpose of this study was to assess critically the complication rates of RFC in centres with both large and limited initial experience, and to establish causes and possible means of prevention and treatment. METHODS: This is an exhaustive review of the world literature (articles and abstracts) up to 31 December 2001; 82 independent reports of RFC of liver tumours were analysed. RESULTS: In total, 3670 patients were treated with percutaneous, laparoscopic or open RFC. The mortality rate was 0.5 per cent. Complications occurred in 8.9 per cent: abdominal bleeding in 1.6 per cent, abdominal infection in 1.1 per cent, biliary tract damage in 1.0 per cent, liver failure in 0.8 per cent, pulmonary complications in 0.8 per cent, dispersive pad skin burn in 0.6 per cent, hepatic vascular damage in 0.6 per cent, visceral damage in 0.5 per cent, cardiac complications in 0.4 per cent, myoglobinaemia or myoglobinuria in 0.2 per cent, renal failure in 0.1 per cent, tumour seeding in 0.2 per cent, coagulopathy in 0.2 per cent, and hormonal complications in 0.1 per cent. The complication rate was 7.2, 9.5, 9.9 and 31.8 per cent after a percutaneous, laparoscopic, simple open and combined open approach respectively. The mortality rate was 0.5, 0, 0 and 4.5 per cent respectively. CONCLUSION: The morbidity and mortality of RFC, while low, is higher than previously assumed. With adequate knowledge, many complications are preventable.

Carcinoma, Hepatocellular↗

PubMed2001

Akt/protein kinase B is constitutively active in non-small cell lung cancer cells and promotes cellular survival and resistance to chemotherapy and radiation.

To evaluate the role of Akt/PKB in non-small cell lung cancer (NSCLC) survival, we analyzed NSCLC cell lines that differed in tumor histology as well as p53, Rb, and K-ras status. Constitutive Akt/protein kinase B (PKB) activity was demonstrated in 16 of 17 cell lines by maintenance of S473 phosphorylation with serum deprivation. Additional analysis of five of 2these NSCLC lines revealed that phosphorylation of S473 and T308 correlated with in vitro kinase activity. Akt/PKB activation was phosphatidylinositol 3-kinase-dependent and promoted survival because the phosphatidylinositol 3 inhibitors LY294002 and wortmannin inhibited Akt/PKB phosphorylation, Akt/PKB activity, and increased apoptosis only in cells with active Akt/PKB. To test whether Akt/PKB activity promoted therapeutic resistance, LY294002 was added with individual chemotherapeutic agents or irradiation. LY294002 greatly potentiated chemotherapy-induced apoptosis in cells with high Akt/PKB levels, but did not significantly increase chemotherapy-induced apoptosis in cells with low Akt/PKB levels. Combined with radiation in cells with active Akt/PKB, LY294002 additively increased apoptosis and inhibited clonogenic growth. These results were extended with transiently transfected Akt/PKB mutants. Transfecting dominant negative Akt/PKB decreased Akt/PKB activity and increased basal apoptosis as well as chemotherapy- and irradiation-induced apoptosis only in cells with high Akt/PKB activity. Conversely, transfecting constitutively active Akt/PKB into cells with low Akt/PKB activity increased Akt/PKB activity and attenuated chemotherapy- and radiation-induced apoptosis. We therefore identify Akt/PKB as a constitutively active kinase that promotes survival of NSCLC cells and demonstrate that modulation of Akt/PKB activity by pharmacological or genetic approaches alters the cellular responsiveness to therapeutic modalities typically used to treat patients with NSCLC.

Apoptosis↗

PubMed2001

Evidence that NADP+ is the physiological cofactor of ADP-L-glycero-D-mannoheptose 6-epimerase.

ADP-L-glycero-D-mannoheptose 6-epimerase is required for lipopolysaccharide inner core biosynthesis in several genera of Gram-negative bacteria. The enzyme contains both fingerprint sequences Gly-X-Gly-X-X-Gly and Gly-X-X-Gly-X-X-Gly near its N terminus, which is indicative of an ADP binding fold. Previous studies of this ADP-l-glycero-D-mannoheptose 6-epimerase (ADP-hep 6-epimerase) were consistent with an NAD(+) cofactor. However, the crystal structure of this ADP-hep 6-epimerase showed bound NADP (Deacon, A. M., Ni, Y. S., Coleman, W. G., Jr., and Ealick, S. E. (2000) Structure 5, 453-462). In present studies, apo-ADP-hep 6-epimerase was reconstituted with NAD(+), NADP(+), and FAD. In this report we provide data that shows NAD(+) and NADP(+) both restored enzymatic activity, but FAD could not. Furthermore, ADP-hep 6-epimerase exhibited a preference for binding of NADP(+) over NAD(+). The K(d) value for NADP(+) was 26 microm whereas that for NAD(+) was 45 microm. Ultraviolet circular dichroism spectra showed that apo-ADP-hep 6-epimerase reconstituted with NADP(+) had more secondary structure than apo-ADP-hep 6-epimerase reconstituted with NAD(+). Perchloric acid extracts of the purified enzyme were assayed with NAD(+)-specific alcohol dehydrogenase and NADP(+)-specific isocitric dehydrogenase. A sample of the same perchloric acid extract was analyzed in chromatographic studies, which demonstrated that ADP-hep 6-epimerase binds NADP(+) in vivo. A structural comparison of ADP-hep 6-epimerase with UDP-galactose 4-epimerase, which utilizes an NAD(+) cofactor, has identified the regions of ADP-hep 6-epimerase, which defines its specificity for NADP(+).

Adenine Nucleotides↗

PubMed2001

Radiofrequency ablation for eradication of pulmonary tumor in rabbits.

BACKGROUND: Radiofrequency ablation (RFA) has emerged as an alternative for surgery in clinical oncology. This animal experiment was conducted to evaluate the feasibility of RFA in the treatment of pulmonary tumor. METHODS: Eighteen rabbits with pulmonary implantation of VX2 tumors were divided into two groups. Group A (n = 12) was treated with RFA by using a cooled-tip electrode technique. Group B (n = 6) received sham operation. The therapeutic efficacy was evaluated by survival rate, magnetic resonance imaging (MRI), postmortem microangiography, and histology. RESULTS: All animals in group B died within 3 months after tumor implantation. Tumor eradication was achieved in 9 of 12 rabbits (75.0%) in group A, of which 4 rabbits survived longer than 3 months free of disease and another 5 rabbits were found free of viable tumor when sacrificed. One rabbit was subjected to incomplete tumor ablation and two rabbits suffered from local tumor relapse and/or lung metastasis. The 3-month survival rate of RFA-treated rabbits was significantly higher (P < 0.01) than that of control rabbits. The typical MRI appearances of the acute RFA lesion consisted of five characteristic concentric zones, which corresponded to central needle track (zone A), tumor coagulation (zone B), pulmonary parenchyma coagulation (zone C), peripheral hemorrhage (zone D), and inflammatory layer (zone E) on histology. CONCLUSIONS: Eradication of pulmonary tumor could be achieved with current RFA technique in rabbits. MRI is a useful modality for assessment of lung tumor ablation.

Angiography↗

PubMed2001

Intracoronary delivery of Gd-DTPA and Gadophrin-2 for determination of myocardial viability with MR imaging.

The aim of this study was to compare intracoronary (i.c.) administration of Gadophrin-2, a necrosis-avid contrast agent (NACA), and nonspecific agent Gd-DTPA for determination of myocardial viability (MV) in acute myocardial infarction (AMI) with MRI. Reperfused AMI was induced in 12 dogs by transcatheter balloon occlusion of coronary artery. In 6 dogs each, Gd-DTPA at 0.1 mmol/kg or Gadophrin-2 at 0.005 mmol/kg was administered into coronary artery by fast bolus (n = 3) or slow infusion (n = 3). Serial ECG-triggered cardiac MRI of T1-weighted segmented turbo fast low-angle shot (FLASH) sequence was conducted and compared with triphenyltetrazolium chloride (TTC) histochemical staining. The contrast ratio and infarct size were quantified and analysed statistically. No cardiovascular side effects were found with local delivery of both agents. After i.c. administration, Gadophrin-2 induced a strong (CR > or = 1.78) and persistent (> or = 10 h) contrast enhancement of infarcted region. The infarct size defined with Gadophrin-2 was almost identical to that with TTC staining throughout the postcontrast period. With a dose 20 times higher, Gd-DTPA also strongly enhanced infarct-to-normal contrast; however, the enhancement diminished with time, i.e. from early strong to later faint enhancement and eventual loss of contrast. The delineated infarct size was also unstable, i.e. from early overestimation to later underestimation and eventual disappearance of the enhanced infarct. In combination with PTCA procedure, i.c. administration of MRI contrast agents may prove useful for post-procedure verification of diagnosis. The NACA-enhanced MRI may serve as an in vivo surrogate of postmortem histochemical staining for determination of MV. Although applicable in clinical setting, cardiac MRI with nonspecific Gd-DTPA is less reliable and should be performed within less than 1 h after contrast.

Animals↗

PubMed2001

An ex vivo study on radiofrequency tissue ablation: increased lesion size by using an "expandable-wet" electrode.

The present comparative study was conducted to validate a newly developed "expandable-wet" electrode for an increased lesion size of radiofrequency ablation (RFA) on excised beef liver. The expandable-wet electrode, which allows interstitial hypertonic saline infusion through retractable curved needles, was compared with "expanded-dry" and "unexpanded-wet" electrodes for RFA lesion size and other parameters. A total of 120 lesions were created under 50 W (groups A-C) and 90 W (groups A'-C') power control mode for 10 min at each ablation site with the following groups: group A and A' of expanded-dry electrode (needles deployed but saline uninfused); group B and B' of unexpanded-wet electrode (saline infused but needle undeployed); and group C and C' of expanded-wet electrode (needles deployed and saline infused). Together with lower impedance and higher power output, the lesion size in group C (5.3+/-0.4 cm) and C' (6.0+/-1.0 cm) were significantly larger (P<0.01) than that in group A (3.3+/-0.3 cm) and A' (2.0+/-0.2 cm), and group B (3.8+/-1.0 cm) and B' (2.6+/-0.4 cm). The RFA lesion size can be significantly enlarged when the expandable electrode is complemented with interstitial hypertonic saline infusion. This design may improve the efficacy of RF tumor ablation.

Animals↗

PubMed2001

Radiofrequency ablation for eradication of renal tumor in a rabbit model by using a cooled-tip electrode technique.

BACKGROUND: Radiofrequency ablation (RFA) has emerged as a potential alternative for surgery in clinical oncology. This animal experiment was conducted to evaluate the feasibility of RFA in the treatment of renal tumor. METHODS: Eighteen rabbits with renal implantation of VX2 tumors were divided into two groups. Group A (n = 12) was treated with RFA by using a cooled-tip RF system at 30 W for 80 to 180 seconds. Group B (n = 6) received a sham operation. The therapeutic efficacy was evaluated by survival rate, magnetic resonance imaging (MRI), and histology. RESULTS: All animals in group B died within 3 months after tumor implantation. Total tumor eradication was achieved in 10 of 12 rabbits (83.3%) in group A, of which 5 rabbits survived longer than 6 months (absolute eradication) and another 5 rabbits were found free of viable tumor when killed (relative eradication). Two rabbits experienced local tumor relapse, lung metastasis, or both. Six-month survival rate of RFA-treated rabbits was significantly higher (P < .01) than that of control rabbits. The typical MRI appearances of the acute RFA lesion consisted of five characteristic concentric zones, which corresponded to central needle track (zone A), tumor coagulation (zone B), renal tissue coagulation (zone C), peripheral hemorrhage (zone D), and inflammatory layer (zone E) on histology. CONCLUSIONS: RFA may become a promising therapy for the treatment of renal tumor. MRI is a useful modality for assessment of renal tumor ablation.

Animals↗