Comparative cytotoxicity of fumonisin B1 in two cell lines derived from normal human bronchial epithelial cells using four distinct bioassay techniques

This study focuses on the cytotoxic effects of fumonisin B₁ (FB₁) on both immortalised and immortalised and subsequently transfected normal human bronchial epithelial (NHBE) cells of human origin using four bioassays. While the MTT, Neutral Red and hexosaminidase colorimetric assays showed little difference between the toxic effects on the two related cell lines, the clonogenic assay, measuring cell survival and proliferation, indicated that FB₁ had a more toxic effect on the nontransfected cells. This kind ofin vitro approach using cells which retain many characteristics of normal cell growth and differentiation can go some way to developing evaluation models for food safety in the case of mycotoxin contamination without resorting totally to whole animal testing. Nevertheless, one or two cytotoxicity tests may be inadequate for a complete appraisal of toxic potential: rather, as wide a range of methodologies as feasible should be employed initially before meaningful conclusions may be drawn.     

Bcl-2 regulates amplification of caspase activation by cytochrome c

Caspases, a family of specific proteases, have central roles in apoptosis [1]. Caspase activation in response to diverse apoptotic stimuli involves the relocalisation of cytochrome c from mitochondria to the cytoplasm where it stimulates the proteolytic processing of caspase precursors. Cytochrome c release is controlled by members of the Bcl-2 family of apoptosis regulators [2] [3]. The anti-apoptotic members Bcl-2 and Bcl-xL may also control caspase activation independently of cytochrome c relocalisation or may inhibit a positive feedback mechanism [4] [5] [6] [7]. Here, we investigate the role of Bcl-2 family proteins in the regulation of caspase activation using a model cell-free system. We found that Bcl-2 and Bcl-xL set a threshold in the amount of cytochrome c required to activate caspases, even in soluble extracts lacking mitochondria. Addition of dATP (which stimulates the procaspase-processing factor Apaf-1 [8] [9]) overcame inhibition of caspase activation by Bcl-2, but did not prevent the control of cytochrome c release from mitochondria by Bcl-2. Cytochrome c release was accelerated by active caspase-3 and this positive feedback was negatively regulated by Bcl-2. These results provide evidence for a mechanism to amplify caspase activation that is suppressed at several distinct steps by Bcl-2, even after cytochrome c is released from mitochondria.     

Development of a novel biosensing system based on the structural change of a polymerized guanine-quadruplex DNA nanostructure

By inserting an adenosine aptamer into an aptamer that forms a G-quadruplex, we developed an adaptor molecule, named the Gq-switch, which links an electrode with flavin adenine dinucleotide-dependent glucose dehydrogenase (FADGDH) that is capable of transferring electron to a electrode directly. First, we selected an FADGDH-binding aptamer and identified that its sequence is composed of two blocks of consecutive six guanine bases and it forms a polymerized G-quadruplex structure. Then, we inserted a sequence of an adenosine aptamer between the two blocks of consecutive guanine bases, and we found it also bound to adenosine. Then we named it as Gq-switch. In the absence of adenosine, the Gq-switch-FADGDH complex forms a 30-nm high bulb-shaped structure that changes in the presence of adenosine to give an 8-nm high wire-shaped structure. This structural change brings the FADGDH sufficiently close to the electrode for electron transfer to occur, and the adenosine can be detected from the current produced by the FADGDH. Adenosine was successfully detected with a concentration dependency using the Gq-switch-FADGDH complex immobilized Au electrode by measuring response current to the addition of glucose.     

Gray matter imaging in multiple sclerosis: what have we learned?

At the early onset of the 20^th century, several studies already reported that the gray matter was implicated in the histopathology of multiple sclerosis (MS). However, as white matter pathology long received predominant attention in this disease, and histological staining techniques for detecting myelin in the gray matter were suboptimal, it was not until the beginning of the 21^st century that the true extent and importance of gray matter pathology in MS was finally recognized. Gray matter damage was shown to be frequent and extensive, and more pronounced in the progressive disease phases. Several studies subsequently demonstrated that the histopathology of gray matter lesions differs from that of white matter lesions. Unfortunately, imaging of pathology in gray matter structures proved to be difficult, especially when using conventional magnetic resonance imaging (MRI) techniques. However, with the recent introduction of several more advanced MRI techniques, the detection of cortical and subcortical damage in MS has considerably improved. This has important consequences for studying the clinical correlates of gray matter damage. In this review, we provide an overview of what has been learned about imaging of gray matter damage in MS, and offer a brief perspective with regards to future developments in this field.