Effects on the accelerating electron bunches due to the presence of sulfur hexafluoride or air in the linac waveguide.

Sulfur hexafluoride gas (SF6) is used as a dielectric insulator in the acceleration process of certain medical linear accelerator waveguides. Nevertheless, some innovative development and investigation cases require intervention in the linear accelerator or, specifically, on the waveguide, which could affect the sealing of the device. In this regard, vacuum sealing systems can be compromised, affecting the properties of the radiation beams produced. The presence of sulfur hexafluoride or air inside the VARIAN 6/100 waveguide was investigated under different pressure conditions and non-uniform electric fields, adapting Monte Carlo simulation techniques for modeling radiation transport coupled with electric fields. Obtained results indicated the suitability of the proposed approach, while comparisons with theoretical approaches and experimental evidence supported the model's consistency.

Effects of hyaluronan on the invasive properties of human breast cancer cells in vitro.

Hyaluronan (HA) is a high molecular weight glycosaminoglycan present mostly in the extracellular matrix (ECM). HA binds to specific receptors such as CD44. Its production is increased at the tumour-stroma interface, including those in breast cancer tumours. It has been suggested that it facilitates invasion of tumour cells into the ECM by a hydrodynamic effect, or by altering tumour cell behaviour. Using in vitro tests we studied the effect of immobilized (iHA) and soluble (sHA) HA on the invasive properties of four human breast cancer cell lines with different levels of CD44 expression. Our results show that iHA acts as an adhesive, haptotactic, and motility stimulating factor for the CD44 positive Hs578T cells and induces the expression of membrane CD44. sHA also changes the motility properties of the Hs578T and MDA-231 cells and increases their CD44 expression. sHA or iHA have no measurable effect on the adhesion, motility or CD44 expression of the ZR-75-1 and MCF-7 breast cancer cells. Our results establish that in high CD44 expressing breast cancer cells HA modulates tumour cell adhesion and motility and also increases the expression of its own receptor, CD44.

Adhesion proteins in the biology of breast cancer: contribution of CD44.

One of the most important features of tumor cell invasion is the ability to establish or modulate adhesion to other cells or to an extracellular matrix, a process mediated by a large number of adhesion proteins. This review examines how CD44 participates in malignant transformation and progression of the breast epithelium. CD44 is a family of cell adhesion glycoproteins generated by alternative splicing of up to 10 variant exons. Discrete CD44 isoforms are overexpressed in different human cancers, including breast cancer. Recent studies, including our own, have shown that CD44 is involved in two of the three steps of the invasive cascade: adhesion to the extracellular matrix and motility. The overexpression of one of the CD44 variants, CD44v6, is a significant component in the malignant transformation of the breast epithelium and its use as a prognostic marker is presently investigated.

CD44 modulates Hs578T human breast cancer cell adhesion, migration, and invasiveness.

CD44 is an adhesion molecule that has been implicated in tumor progression of epithelial and nonepithelial tumors. One of its variants, CD44v6, is involved in the production of experimental metastasis. Previous reports have indicated that in human breast cancer the overexpression of CD44, and moreover the presence of CD44v6, correlated with poor prognosis. This study focuses on the role of these molecules in in vitro invasion of breast cancer cells. The effect of antibodies against all CD44 isoforms and CD44v6 was evaluated in different in vitro experimental assays that are closely related to tumor cell invasion in vivo: adhesion to hyaluronan and purified extracellular matrix components; cell motility; haptotaxis; and invasion of purified extracellular matrix components. The highly metastatic human breast cancer cell line Hs578T was used in all assays. Our results show that both antibodies have a blocking effect on cell migration, on haptotatic migration, on in vitro invasion, and on adhesion to hyaluronan and purified extracellular matrix components. In conclusion, our data show that, in addition to its participation in adhesion to components of the extracellular matrix, CD44v6 is involved in the motility and in invasion of tumoral cells.

MRI of pseudocoarctation of the aorta: morphological and cine-MRI findings.

We report a case of pseudocoarctation of the thoracic aorta diagnosed by magnetic resonance imaging. Morphological spin-echo findings and cine-MRI performed by gradient-echo multiphase images are reported. No other more invasive examinations were needed to establish the diagnosis of pseudocoarctation and to differentiate from other aortic abnormalities.

Correlation between cell differentiation stage, types of invasion, and hematogenous metastasis in experimental rhabdomyosarcomas.

Cancer malignancy is directly related to invasiveness and metastasis and inversely related to the degree of tumor differentiation. The relation between the stage of cell differentiation and the types of invasion leading to metastasis is not entirely clear. Intramuscularly transplanted rat rhabdomyosarcomas are good models to study cell differentiation, invasion, and metastasis. Rat rhabdomyosarcoma cell lines (SMF-Ai, SMF-Da, and RMS-B and its clones) with defined invasive and metastatic potentials have been established. The stage of myogenic differentiation was evaluated morphologically and by immunohistochemistry. Invasiveness was evaluated according to the infiltration of muscle fibers and basal lamina. The SMF-Ai line is highly invasive and metastatic. It is composed of premyoblasts that were involved in intercellular, translaminar, and transcellular invasion of muscle fibers. The SMF-Da line is noninvasive and nonmetastatic. It is composed of myoblasts. The RMS-B line and its clones were at different stages of differentiation and they differed in their invasiveness and metastatic potentials. In highly invasive and metastatic clones (RMS-Bg and RMS-Bc), premyoblasts were involved in translaminar invasion. Clones composed of myoblasts, rhabdomyoblasts, and myotubes only showing intercellular invasion did not present hematogenous metastasis. Our results demonstrate a correlation between premyoblastic stage of differentiation and translaminar invasion. The presence of translaminar invasion is directly related to hematogenous metastatic ability of rat rhabdomyosarcomas.

Aortic calcification and renal cysts demonstrated by CT in a teenager with Alagille syndrome.

Alagille syndrome, or arteriohepatic dysplasia, is a disorder characterized by paucity of intrahepatic bile ducts, peculiar facies and skeletal anomalies. We report a typical case of this syndrome in an 18-year-old girl, in whom abdominal CT showed bilateral renal cysts and aortic wall calcification, findings unreported in the radiological literature.