Mechanisms of cancer cell invasion

The movement of cancer cells into tissue surrounding the tumour and the vasculature is the first step in the spread of metastatic cancers. Recent advances in imaging, the use of 3D model systems and the application of microarray technologies have yielded new insights into these processes. This work has challenged our views about what causes cancer cells to become motile in the first place, and has demonstrated that cancer cells can move in many different ways.     

Changes in Nucleic Acid Metabolism of Excised Barley Leaves During Senescence and the Effect of Kinetin on these Changes

The changes in the amount, rale of synthesis and the nucleotide composition of different RNA fractions in excised barley leaves floated on water or kinetin (10 mg/l) in the dark were examined. In excised leaves floated on water all nucleic acid components declined and these declines were retarded by kinetin. Barley leaves floated on water showed a stimulation of ³²P incorporation into various RNA fractions within 48 hours followed by a decline after 96–144 hours. The leaves floated on kinetin, however, showed an even higher incorporation of ³²P into UNA by 48 hours which remained at a comparatively higher level throughout the experiment. In spite of the above changes in RNA synthesis significant differences in the ³²P sucrose gradient profiles or in the ³²P nucleotide composition of UNA from water and kinetin floated leaves were not noted. The results of this study show that important changes in nucleic acid metabolism occur during the early stages of leaf senescence and that alterations in nucleic acid metabolism during senescence and during kinetin treatment may involve quantitative and only subtle qualitative changes.     

Roles of phosphatidylinositol 3-kinase and osteopontin in steatosis and aminotransferase release by hepatocytes treated with methionine-choline-deficient medium

Feeding mice a methionine and choline-deficient (MCD) diet serves as an experimental animal model for nonalcoholic steatohepatitis (NASH). In the present study we examined the effect of exposing AML-12 hepatocytes to MCD culture medium in regard to mechanisms of steatosis and alanine amino-transferase (ALT) release. Cells exposed to MCD medium developed significant and progressive steatosis from 6 to 24 h and also had significantly increased loss of ALT into the medium at 18 and 24 hours of incubation. No increased oxidative injury or cell death was observed. Osteopontin (OPN) mRNA in cells and protein expression in medium were significantly increased during 6-24 hours of incubation. MCD medium treatment also resulted in activation of PI3-kinase by 30 minutes and its downstream target p-Akt within 1hour of incubation. Steatosis was associated with increased expression of microsomal triglyceride transfer protein (MTTP) mRNA and increased ALT release with over expression of ALT mRNA, all of which were completely prevented by inhibition of PI3-kinase (LY294002). Blocking OPN signaling by treating with anti-OPN or anti-beta3-integrin antibody prevented the increased ALT release while only partially prevented the increased ALT mRNA expression, but had no effect on either steatosis or MTTP expression. In conclusion, incubation of cultured hepatocytes with MCD medium results in cellular steatosis and OPN dependent ALT release. PI3-kinase plays a central role in signaling the MCD medium-induced steatosis and increased OPN expression, whereas OPN appears to play a role in signaling hepatocyte ALT release but not steatosis.     

Enzymatic synthesis of chiral intermediates for pharmaceuticals

There has been an increasing awareness of the enormous potential of microorganisms and enzymes for the transformation of synthetic chemicals with high chemo-, regio- and enatioselective manner. Chiral intermediates are in high demand by pharmaceutical industries for the preparation bulk drug substances. In this review article, microbial/enzymatic processes for the synthesis of chiral intermediates for antihypertensive drugs, melatonin receptor agonists, and beta3-receptor receptor agonists are described.     

RasGRF suppresses Cdc42-mediated tumour cell movement, cytoskeletal dynamics and transformation

Individual tumour cells move in three-dimensional environments with either a rounded or an elongated 'mesenchymal' morphology. These two modes of movement are tightly regulated by Rho family GTPases: elongated movement requires activation of Rac1, whereas rounded/amoeboid movement engages specific Cdc42 and Rho signalling pathways. In siRNA screens targeting the genes encoding guanine nucleotide exchange factors (GEFs), we found that the Ras GEF RasGRF2 regulates conversion between elongated- and rounded-type movement. RasGRF2 suppresses rounded movement by inhibiting the activation of Cdc42 independently of its capacity to activate Ras. RasGRF2 and RasGRF1 directly bind to Cdc42, outcompeting Cdc42 GEFs, thereby preventing Cdc42 activation. By this mechanism, RasGRFs regulate other Cdc42-mediated cellular processes such as the formation of actin spikes, transformation and invasion in vitro and in vivo. These results demonstrate a role for RasGRF GEFs as negative regulators of Cdc42 activation.     

Role of PKCα−p38MAPK−Giα axis in peroxynitrite-mediated inhibition of β-adrenergic response in pulmonary artery smooth muscle cells

In the context of cross-talk between transmembrane signaling pathways, we studied the loci within the β-adrenergic receptor/G protein/adenyl cyclase system at which PKC exerts regulatory effects of peroxynitrite (ONOO^?) on isoproterenol stimulated adenyl cyclase activity in pulmonary artery smooth muscle cells. Treatment of the cells with ONOO^? stimulated PKC-α activity and that subsequently increased p³⁸MAPK phosphorylation. Pretreatment with Go6976 (PKC-α inhibitor) and SB203580 (p³⁸MAPK inhibitor) eliminated ONOO^? caused inhibition on isoproterenol stimulated adenyl cyclase activity. Pretreatment with Go6976, but not SB203580, prevented ONOO^? induced increase in PKC-α activity. Studies using genetic inhibitors of PKC-α (PKC-α siRNA) and p³⁸MAPK (p³⁸MAPK siRNA) also corroborated the findings obtained with their pharmacological inhibitors in eliminating the attenuation of ONOO^? effect on isoproterenol stimulated adenyl cyclase activity. This inhibitory effect of ONOO^? was found to be eliminated upon pretreatment of the cells with pertussis toxin thereby pointing to a G_i dependent mechanism. This hypothesis was reinforced by G_iα phosphorylation as well as by the observation of the loss of the ability of Gpp(NH)p (a measure of G_i mediated response) to stimulate adenyl cyclase activity upon ONOO^? treatment to the cells. We suggest the existence of a pertussis toxin sensitive G protein (G_i)-mediated mechanism in isoproterenol stimulated adenyl cyclase activity, which is regulated by PKCα-p³⁸MAPK axis dependent phosphorylation of its α-subunit (G_iα) in the pulmonary artery smooth muscle cells.     

Cytomixis—a unique phenomenon in animal and plant

Cytomixis is reported to be a uniform phenomenon in the context of fertilization during spermatogenesis of animals and in some lower groups of plants where oogamous reproduction prevails. However, the phenomenon is versatile in flowering taxa as it lacks uniformity in occurrences, causes, formation of intercellular bridges, involvement of number of cells in a cluster, evolutionary significance among others. A review on cytomixis is conducted with an objective that it may offer a scope to unravel some of the ambiguities associated with it and provide further information on cell, reproductive, structural and evolutionary biology.