[Intracranial artifact un magnetic resonance caused by embolization of microscopic metallic fragment]. / Artefacto intracraneal en resonancia magnética causado por embolización de fragmentos metálicos microscópicos.

Magnetic resonance imaging (MRI) artifacts have been described in many articles published in the literature. We present the case of a 72 year old man who was admitted due to left inferior limb weakness. MRI imaging demonstrated an acute right infarction of the right posterior cerebral artery. In the right frontal lobe a metallic artifact was demonstrated as well. The artifact showed a central signal void and it was surrounded by a high signal intensity rim. His aortic valve had been replaced 12 years earlier. This indicates that the artifact is in fact due to a small metallic fragment embolization during cardiac surgery.

Direct antiproliferative effects of melatonin on two metastatic cell sublines of mouse melanoma (B16BL6 and PG19).

The effects of melatonin on the growth of two highly tumorigenic rodent melanoma cells were studied in vitro. PG19, an amelanotic mouse melanoma cell line, and B16BL6, a melanotic melanoma cell line selected for its invasive potential in vitro, were cultured in the presence of different concentrations of melatonin (10 microM to 0.1 pM). Five days later, viable cells were determined in a haemocytometer by the trypan blue exclusion test. Melatonin at concentrations of 1 nM and 10 pM (within the range of concentrations that correspond to physiological night-time and daytime levels in human blood) significantly inhibited proliferation in both melanoma cell lines. Subphysiological (0.1 pM) or supraphysiological (10 microM to 100 nM) concentrations of melatonin lacked this effect. These results support the hypothesis that, at physiological concentrations, melatonin exerts a direct inhibitory effect on PG19 and B16BL6 cells proliferation.