The effect of all-trans retinoic acid (ATRA) on the expression of vascular endothelial growth factor (VEGF) and VEGF receptors of human colon cancer LoVo cell line

All-trans retinoic acid (ATRA) was found to inhibit cell growth, induce differentiation and enhance apoptosis in a variety of malignant solid tumors. Retinoic acid is effective in inhibiting the expression of vascular endothelial growth factor (VEGF) in some cancer. In this study, we investigated the effect of ATRA on the expression of VEGF and its receptors in LoVo cells, and its possible mechanisms. LoVo cells were treated with ATRA at different concentrations for different time, and with exogenous recombinant human VEGF165 or VEGF165 + ATRA. Cell viability was measured by microtitration (MTT) assay. Cell cycle and apoptosis were evaluated by flow cytometry (FCM). The expression of VEGF in LoVo cells were detected by ELISA technique and Western blot, and its receptors by flow cytometry. ATRA greatly inhibited the proliferation of LoVo cells in dose- and time-dependent manners; inhibition rate of the cells decreased significantly after treatment with ATRA. ATRA could dose-dependently block the VEGF165-induced cell growth. FCM results show that ATRA induced apoptosis of LoVo cells with concomitant decrease of expressed VEGF and its receptors. The mechanism involved in down regulation of VEGF and its receptors may be related to apoptosis. ATRA could also disturb the stimulating effect of VEGF165 on the growth of LoVo cells. These results suggest that ATRA can delay growth of LoVo cells by inhibiting the paracrine and autocrine pathways.Key words: All-trans retinoic acid, LoVo cells, vascular endothelial growth factor, vascular endothelial growth factor (VEGF) receptors

Absolute stability of time-varying delay Lurie indirect control systems with unbounded coefficients

This paper investigates the absolute stability problem of time-varying delay Lurie indirect control systems with variable coefficients. A positive-definite Lyapunov-Krasovskii functional is constructed. Some novel sufficient conditions for absolute stability of Lurie systems with single nonlinearity are obtained by estimating the negative upper bound on its total time derivative. Furthermore, the results are generalised to multiple nonlinearities. The derived criteria are especially suitable for time-varying delay Lurie indirect control systems with unbounded coefficients. The effectiveness of the proposed results is illustrated using simulation examples

Fossilized melanosomes and the colour of Cretaceous dinosaurs and birds

Spectacular fossil remains from the Early Cretaceous Jehol Group of northeastern China have greatly expanded our knowledge of the diversity and palaeobiology of early birds and dinosaurs, and contributed to understanding of the origin of birds, of flight, and of feathers. Pennaceous (vaned) feathers and integumentary filaments are preserved in birds and non-avian theropod dinosaurs, but little is known of their microstructure. Here we report that melanosomes (colour-bearing organelles) are not only preserved in the pennaceous feathers of early birds, but also in an identical manner in filamentous integuments of non-avian dinosaurs, thus refuting recent claims that the filaments are partially decayed dermal collagen fibres. Examples of both eumelanosomes and phaeomelanosomes have been identified, often preserved in life position within the partially degraded fossils of feathers and filaments. Furthermore, the data here provide the first empirical evidence for reconstructing the colours and colour patterning of these extinct birds and theropod dinosaurs: for example, the stripes on the tail of the theropod dinosaur Sinosauropteryx can reasonably be inferred to have exhibited chestnut to rufous tones