Biomedical subjects

David Castel

Publications and source records attributed to David Castel.

12 recordsLinked to original sources

PubMed2006

Magnetic resonance-guided focused ultrasound surgery (MRgFUS): ablation of liver tissue in a porcine model.

BACKGROUND: Liver surgery is technically demanding and is considered a major procedure with relatively high morbidity rates. Magnetic resonance-guided focused ultrasound surgery (MRgFUS) uses focused ultrasonic energy to create a heat coagulation lesion, which can be achieved in a totally controlled, very accurate manner (<1 mm). The aim of this study was to evaluate the safety and accuracy of non-invasive focal ablation of liver tissue achieved by consecutive MRgFUS sonications. MATERIALS AND METHODS: Six MRgFUS procedures were performed in five pigs under general anesthesia, with the ExAblate 2000 system (InSightec, Israel). Real-time imaging and temperature mapping (Signa Twinspeed 1.5T, GEHC, USA) enabled the immediate evaluation of the results of each sonication. Different foci were chosen within the liver. These mock lesions were ablated by several sonications, each of them performed during 20-30 s of apnea. Between sonications, the pigs were normally ventilated. The pigs were sacrificed 3-21 days after the procedure and their livers were examined. RESULTS: The MRgFUS created complete tissue destruction of mock lesions in different areas of the pig's liver. The lesion sizes in each animal varied according to the number of sonications used and the extent of overlap between adjacent sonications. The lesion ranged in size from 1.5 cm x 1.5 cm x 2.0 cm to 5.5 cm x 4.5 cm x 2.0 cm. There was no morbidity. CONCLUSIONS: MRgFUS under general anesthesia is a safe, completely non-invasive technology for the ablation of liver tissue. Liver tissue can be ablated in a very accurate manner, based on the pre-treatment planning on the MR images. The MR imaging characteristics, including real-time temperature mapping, enable real-time control of every step of the ablation process. Mechanical ventilation with intermittent periods of apnea is a technique that overcomes the problem of the respiratory movements of the liver.

Animals↗

PubMed2006

Cell microarrays in drug discovery.

There is an increasing need for systematic cell-based assays in a high-throughput screening (HTS) format to analyze the phenotypic consequences of perturbing mammalian cells with drugs, genes, interfering RNA. Taking advantage of the recent progress in microtechnology, new cell microarrays are being developed and applied to a large range of issues in metazoan cells. This article compares different approaches and evaluates their potential use in the drug discovery process. Although still an emerging technology, cell microarrays hold great promise to optimize the efficiency:cost ratio in cell-based HTS.

Animals↗

PubMed2006

Low-intensity ultrasound induces angiogenesis in rat hind-limb ischemia.

We investigated the effect of low-intensity ultrasound (US) on tissue blood flow and angiogenesis after limb ischemia in vivo. Rats underwent surgical ligation of the femoral or the iliac arteries. Half the animals were exposed to low-intensity US (0.05 W/cm2) during three consecutive sessions. At 3 weeks postsurgery, limb perfusion was assessed using laser Doppler and angiography. Immunostaining and vascular endothelial growth factor (VEGF) messenger ribonucleic acid (mRNA) expression were performed 7 d postsurgery. US irradiation significantly improved limb perfusion in both ischemic models (p = 0.04). Angiography showed increased blood vessels in the moderate ischemia (p = 0.01), but not in the severe ischemia (p = 0.19). Histology demonstrated a significantly higher number of blood vessels and proliferating cells in US-irradiated moderate and severe ischemia (p = 0.002 and p = 0.03, respectively). VEGF mRNA was significantly higher in moderate ischemia (p = 0.02). No differences in apoptotic cell death were evident in the models. Low-intensity US significantly improved tissue blood flow and angiogenesis, irrespective of the extent of the ischemia. (E-mail: ).

Actins↗

PubMed2006

Evaluation of the pro-angiogenic effect of factor XIII in heterotopic mouse heart allografts and FXIII-deficient mice.

Thrombin-activated Factor XIII (FXIIIa), a plasma transglutaminase, stabilizes fibrin clots by crosslinking fibrin chains. FXIIIa was previously shown by us to exhibit proangiogenic activity associated with downregulation of thrombospondin-1, phosphorylation of vascular endothelial growth factor receptor 2 (VEGFR-2), and upregulation of c-Jun. In the current study, we evaluated the proangiogenic effect of FXIIIa in two murine models: a neonatal heterotopic cardiac allograft model in normal mice, and a Matrigel plug model in FXIII-deficient mice. In the neonatal cardiac allograft model, the number of new vessels as well as graft viability (contractile performance) was significantly higher in FXIIIa-injected animals than in controls. A significant increase in the level of c-Jun mRNA and a significant decrease in the level of TSP-1 mRNA were observed in heart allografts treated with FXIIIa. A marked decrease in TSP-1 protein expression was observed within the endothelial cells of hearts treated with FXIIIa. In the Matrigel plug model, FXIII-deficient mice showed a significantly decreased number of new vessels compared to that of the control mice, and the number of vessels almost reached normal levels following addition of FXIIIa. The results of this study provide substantial in vivo evidence for the proangiogenic activity of FXIIIa.

Angiogenesis Inducing Agents↗

PubMed2005

Human umbilical cord blood-derived CD133+ cells enhance function and repair of the infarcted myocardium.

The use of adult stem cells for myocardial tissue repair might be limited in elderly and sick people because their cells are depleted and exhausted. The present study was conducted to explore the potential of human umbilical cord blood (UCB) CD133+ progenitor cells for myocardial tissue repair in a model of extensive myocardial infarction (MI). CD133+ progenitor cells were isolated from newborn UCB. Cells (1.2-2 x 10(6)) or saline (control) was infused intravenously 7 days after permanent coronary artery ligation in athymic nude rats. Left ventricular (LV) function was assessed before and 1 month after infusion by echocardiography. Tracking of human cells was performed by fluorescent in situ hybridization for human X and Y chromosomes or by immunostaining for HLA-DR or HLA-ABC. One month after delivery, LV fractional shortening improved by 42 +/- 17% in cell-treated hearts and decreased by 39 +/- 10% in controls (p = .001). Anterior wall thickness decreased significantly in controls but not in treated hearts. Microscopic examination revealed that the UCB cells were able to migrate, colonize, and survive in the infarcted myocardium. Human cells were identified near vessel walls and LV cavity and were occasionally incorporated into endothelial cells in six of nine cell-treated animals but not in controls. Scar tissue from cell-treated animals was significantly populated with autologous myofibroblasts as indicated by colocalization of HLA-DR and alpha-smooth muscle actin staining. In conclusion, the present work suggests that, after MI, intravenous delivery of human UCB-derived CD133+ cells can produce functional recovery by preventing scar thinning and LV systolic dilatation.

AC133 Antigen↗

PubMed2005

Id2 reverses cell cycle arrest induced by {gamma}-irradiation in human HaCaT keratinocytes.

Id2 plays a key role in epithelial cells, regulating differentiation, the cell cycle, and proliferation. Because human skin constantly renews itself and is the first target of irradiation, it is of primary interest to evaluate whether such a gene may be regulated in keratinocytes exposed to ionizing radiation. We show here that Id2 is induced in response to gamma-irradiation and have investigated the consequence of this regulation on cell fate. Using RNA interference, we observed that Id2 extinction significantly reduces cell growth in human keratinocytes through the control of the G(1)-S transition of the cell cycle. We have investigated whether the impact of Id2 on the cell cycle may have a physiological role on the cell's ability to cope with radiative stress. Indeed, when Id2 is down-regulated through interfering RNA, cells are more sensitive to irradiation. Conversely, when Id2 is overexpressed, this somehow protects the cell. We propose that Id2 favors reentering the cell cycle after radiation-induced cell cycle arrest to permit the recovery of keratinocytes exposed to ionizing radiation.

Cell Cycle↗

PubMed2005

[Cell microarrays and functional genomics].

With the complete sequencing of the human genome, research priorities have shifted from the identification of genes to the elucidation of their function. Methods currently used by scientists to characterize gene function, such as knock-out mice, are based upon loss of protein function and analysis of the resulting phenotypes to infer a potential role for the protein under scrutiny. Until now, these methods have been successful but time consuming and only a few genes at a time could be analyzed. Cell microarrays allow to simultaneously transfect thousands of different nucleic acid molecules, RNA or DNA, into adherent cells. It is then possible to analyze a large pallet of resulting phenotypes in clusters of transfected cells. We are currently manufacturing cell microarrays with collections of full-length cDNA cloned in expression vectors (gain of function analyses) or siRNA (loss of function studies) to unravel function of genes involved in differentiation and proliferation of human cells. Although there are still some technological difficulties to overcome, the potential for cell microarrays to speed up functional exploration of genomes is very promising.

Cells, Cultured↗

PubMed2005

Impaired wound healing in factor XIII deficient mice.

Factor XIII that stabilizes fibrin clots in the final stages of blood coagulation also participates in wound healing, as can be inferred from a delay in wound repair in some patients with inherited FXIII deficiency. In this study we evaluated the effect of FXIII on wound healing in FXIII-deficient mice. Three groups of mice (n = 10) were employed: control group, FXIII-deficient group and FXIII-deficient group treated with FXIII concentrate. Excisional wounds were left unsutured and undressed, and mice were followed for eleven days. FXIII-deficient mice exhibited impaired wound healing as has been demonstrated by 15%, 27% and 27% decrease in percentage of wound closure on day 4, 8 and 11, respectively. On day 11 complete healing was observed in control (100% closure), 73.23% in FXIII-deficient and 90.06% in FXIII deficient/FXIII-treated groups (p = 0.007 by ANOVA and p = 0.001 by t-test between control and FXIII-deficient groups). Scoring system representing maturation rate of the wounds showed that the scores for the control, FXIII-deficient and FXIII deficient/FXIII treated groups were 94.9 +/- 4.7, 61.5 +/- 14.5 and 94.5 +/- 6.4, respectively (p < 0.001 by ANOVA). Histological analysis of the lesions performed at day 11 disclosed delayed reepithelization and necrotized fissure in FXIII-deficient mice and normal healing in FXIII-deficient/FXIII-treated mice. The findings of this study confirm that in FXIII-deficient mice wound healing is delayed and the cellular and tissue defects can be corrected by treatment with FXIII, providing evidence for the essential role of FXIII in wound repair and remodeling.

Analysis of Variance↗

PubMed2004

Quantitative analysis of highly parallel transfection in cell microarrays.

As more genomes are sequenced, we are facing the challenge of rapidly unraveling the functions of genes. To that end, cell microarrays have recently been described that transfect thousands of nucleic acids in parallel and can be used to analyze the phenotypic consequences of such perturbations. As many parameters can influence the efficacy of transfection in such a format, we describe some important features in manufacturing cell microarrays that may improve reliability and efficiency of both plasmid DNA and siRNA transfection. We have also developed image analysis software that allows automatic detection of cell clusters, quantification of transfection efficiency and levels of expression/extinction of genes. Along with cell microarrays, this bioinformatic tool should expedite functional exploration of the human genome.

Automation↗

PubMed2003

Characterization of arterial stenosis and elasticity by analysis of high-frequency pressure wave components.

We describe a novel method for assessing stenosis severity based on pressure wave measurements. Pressure waves for several degrees of stenosis at different distances proximal to the stenosis were recorded from in vitro and in vivo models. Signal analysis was performed using power spectral density, and radial compliance was also measured. Pressure wave components at the acoustic frequency band (400-2500Hz) changed gradually and were dependent upon the distance from the stenosis and its severity. The shift of the pressure components could also demonstrate the elastic properties of tubes and arteries and explain the effect of a bifurcation in the system.

Arterial Occlusive Diseases↗

PubMed2002

Dalteparin sodium (fragmin) administration following acute infarction does not affect myocardial perfusion and function in swine.

BACKGROUND: Heparin and low molecular weight heparin (LMWH) derivatives are considered angiogenic factors in ischemic and infarcted myocardium. However, the effect of dalteparin sodium (fragmin, a LMWH derivative) on angiogenesis post infarction has not yet been investigated.Purpose. To assess the effect of systemically-administered dalteparin sodium on left ventricular perfusion and function during remodeling in swine subjected to acute microembolization infarction (MI).Methods. MI was induced in 12 anesthetized female pigs which randomly received dalteparin sodium (12,500U) or placebo through intra-peritoneal osmotic pump, for one week, beginning immediately after the MI. Myocardial perfusion and function were measured using radionuclear scan and echocardiography, respectively, at baseline, immediately post MI, and at 2 and 4 weeks post MI. Dobutamine stress echocardiography was performed 4 weeks post MI. Serum level of basic fibroblast growth factor (bFGF) was analyzed using a commercially available ELISA kit.Results. No differences were observed in myocardial perfusion at all time points following MI. No significant changes were observed in myocardial function and wall motion during the 4 weeks follow-up period, or after dobutamine administration. Serum bFGF did not change throughout the study period.Conclusion. Under the setting of the current experiment, one week of dalteparin sodium administration does not affect myocardial perfusion and function following acute infarction in swine, either at rest or following pharmacological stress.

Animals↗

PubMed2002

The area of the pressure-flow loop for assessment of arterial stenosis: a new index.

This study describes a novel method for assessing stenotic severity, based on simultaneous pressure and flow wave measurements. Pressure and flow measurements were performed in latex and rubber tubes, and in a clinically-used vascular graft. Pressure waves were recorded at several degrees of stenosis and at different distances proximal to the stenosis. Pressure wave versus flow wave was plotted. Internal pressure-flow loop area (PFLA), loop slope and pressure-axis intercept were calculated. Values of these three indices significantly increased with increasing degrees of stenosis P < 0.001). Similar phenomenon was observed during in-vivo experiments. Polynomial functions were fitted, resulting in an excellent PFLA variable/ percent stenosis correlation, independent of distance between sensor and stenosis (R2 > 0.96). In addition, tube compliance was measured and found to correlate with the polynomial coefficients (/R/ > 0.9). This innovative approach could significantly contribute to detecting and evaluating arterial stenoses, and to characterize the elasticity of the artery.

Animals↗