Pten constrains centroacinar cell expansion and malignant transformation in the pancreas

To determine the role of the phosphatidylinositol 3-kinase (PI3-K) pathway in pancreas development, we generated a pancreas-specific knockout of Pten, a negative regulator of PI3-K signaling. Knockout mice display progressive replacement of the acinar pancreas with highly proliferative ductal structures that contain abundant mucins and express Pdx1 and Hes1, two markers of pancreatic progenitor cells. Moreover, a fraction of these mice develop ductal malignancy. We provide evidence that ductal metaplasia results from the expansion of centroacinar cells rather than transdifferentiation of acinar cells. These results indicate that Pten actively maintains the balance between different cell types in the adult pancreas and that misregulation of the PI3-K pathway in centroacinar cells may contribute to the initiation of pancreatic carcinoma in vivo.     

Ferromagnetic materials in patients: detection before MR imaging

A number of surgical clips and other metallic materials embedded within patients have ferromagnetic properties that present a potential hazard when in the strong fields associated with magnetic resonance imaging. Several types of magnetometers and metal detectors were investigated as possible pre-imaging screening devices. The sensitivities and costs of these devices are given.     

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Current aspects of forensic lawFrom October 2004 to March 2005

     

高压培养对血管内皮细胞t-PA和PAI-1的影响及卡托普利干预的效果

目的：高血压常伴有纤溶功能的异常,但其机制尚不清楚。本研究拟观察高静水压培养对人脐静脉内皮细胞（HUVECs）t-PA和PAI-1的影响以及卡托普利的干预效果,并探讨其可能的作用机制。方法：选用第4～6代HU-VECs,接种于24孔培养板中。依培养压力分为3组：大气压组（0mmHg）,中压组（90mmHg）,高压组（180mmHg）。在同一压力组,根据不同药物干预又分为两个亚组。即对照组（Ctrl）和卡托普利组（Cap,10^-5mol/L）。每组6份标本。采用ELISA法测定上清液t-PA和PAI-1的抗原浓度,并用细胞内总蛋白进行标化（单位：ng/μg proteins）。同时测定细胞内Ca^2＋浓度（nmol/L）。结果：与大气压组相比,中压和高压组t-PA浓度均显著降低,PAI-1浓度显著增高,t-PA/PAI-1比值显著降低,[Ca^2＋]i也显著增高。卡托普利对大气压组的t-PA、PAI-1和[Ca^2＋]i无显著影响,但在两个高压组,卡托普利显著升高t-PA浓度,显著降低PAI-1浓度,t-PA/PAI-1比值显著升高,[Ca^2＋]i显著地降低。结论：高静水压可损害内皮细胞的纤溶功能,而卡托普利的干预可降低高压所升高的[Ca^2＋]i,并改善高静水压对内皮细胞纤溶功能的影响。     

Dynamic holographic imaging of the beating human heart

Background--Currently, the reporting and archiving of echocardiographic data suffer from the difficulty of representing heart motion on printable 2-dimensional (2D) media. Methods and Results--We studied the capability of holography to integrate motion into 2D echocardiographic prints. Images of normal human hearts and of a variety of mitral valve function abnormalities (mitral valve prolapse, systolic anterior motion of the mitral leaflets, and obstruction of the mitral valve by a myxoma) were acquired digitally on standard echocardiographic machines. Images were processed into a data format suitable for holographic printing. Angularly multiplexed holograms were then printed on a prototype holographic "laser" printer, with integration of time in vertical parallax, so that heart motion became visible when the hologram was tilted up and down. The resulting holograms displayed the anatomy with the same resolution as the original acquisition and allowed detailed study of valve motion with side-by-side comparison of normal and abnormal findings. Comparison of standard echocardiographic measurements in original echo frames and corresponding hologram views showed an excellent correlation of both methods (P<0.0001, r2=0.979, mean bias=2.76 mm). In this feasibility study, both 2D and 3D holographic images were produced. The equipment needed to view these holograms consists of only a simple point-light source. Conclusions--Holographic representation of myocardial and valve motion from echocardiographic data is feasible and allows the printing on a 2D medium of the complete heart cycle. Combined with the recent development of online holographic printing, this novel technique has the potential to improve reporting, visualization, and archiving of echocardiographic imaging.