Differential effects of trichostatin A on gelatinase A expression in 3T3 fibroblasts and HT-1080 fibrosarcoma cells: implications for use of TSA in cancer therapy

Trichostatin A (TSA) is a histone deacetylase (HDAC) inhibitor with potential in cancer therapeutics. In a recent communication, we demonstrated that TSA is a selective, potent inhibitor of gelatinase A in 3T3 fibroblasts. In the present study, we extend these observations and examine the effects of TSA in 3T3 fibroblasts compared to HT-1080 fibrosarcoma cells with respect to gelatinase A expression, cell viability, and apoptosis. We find that while expression of gelatinase A in 3T3 fibroblasts is exquisitely sensitive to inhibition by TSA, expression of this enzyme in HT-1080 cells is minimally affected by this compound. Moreover, we show that TSA is pro-apoptotic in HT-1080 cells, but is anti-apoptotic in 3T3 cells. We propose a two-pronged model for the therapeutic action of TSA. On the one hand TSA selectively decreases cancer cell viability, while enhancing the viability of stromal cells. On the other hand, by selectively decreasing gelatinase A expression in stromal but not cancer cells, TSA acts to control metastatic potential by reducing the ability of metastatic cells to recruit stromal cells to secrete gelatinase A.     

Effect of aromatic cedar mulch on Argentine ant (Hymenoptera: Formicidae) foraging activity and nest establishment

In the laboratory, Argentine ant, Linepithema humile (Mayr), mortality was positively correlated to the length of an aromatic cedar mulch section that had to be crossed before food could be reached. When ants could access food without crossing the mulch, mortality was not correlated to mulch section length. In the field, Argentine ants showed a tendency to avoid aromatic cedar mulch as a nesting substrate. In plant beds alongside buildings the number of ant nests (pockets containing brood) found was not significantly different between aromatic cedar and cypress mulch. However, when pine straw mulch around oak trees was replaced with aromatic cedar or cypress mulch, a similar number of ant nests was found in the cypress mulch as in the original pine straw, whereas numbers in aromatic cedar mulch were significantly lower. Also, fewer ants were trailing on the trees surrounded by aromatic cedar mulch compared with cypress mulch or the original pine straw. The number of ants attracted to apple jelly baits placed alongside the buildings did not differ between mulch types; neither did the number of ant trails crossing the mulch beds around the buildings. We suggest that aromatic cedar mulch may help control Argentine ants and reduce insecticide input when applied in combination with conventional control methods.     

Xenobiotic conjugation systems in deer compared with cattle and rat

The ability of cattle and deer liver to catalyse xenobiotic conjugation reactions was investigated and compared with that of the rat. Marked differences in the activity of these enzymes were noted between the domestic animals and rats. Hepatic microsomal epoxide hydrolase activity in cattle and deer, determined using benzo[a]pyrene 4,5-oxide as substrate, was nearly twice that of the rat. In contrast, glutathione S-transferase activity in hepatic cytosol, determined with 1-chloro-2,4-dinitrobenzene as substrate, was significantly lower in the cattle and deer. When 1,2-dichloro-4-nitrobenzene served as the accepting substrate, no activity was detectable in the cattle and deer. Similarly, glutathione reductase activity and total glutathione levels were markedly lower in the cattle and deer compared with the rat. Cytosolic sulfotransferase activity, monitored using 2-naphthol as substrate, was higher in cattle compared with the rat. Finally, microsomal UDP-glucuronosyl transferase activity, determined using 1-napththol as substrate, did not differ significantly among the three species.     

Expression and purification of biologically active IGF-binding proteins using the LCR/Mel expression system

The anabolic effects and bioavailability of insulin-like growth factors I and II (IGF-I, IGF-II) are regulated in part by a family of IGF-binding proteins (IGFBPs). There are six known members of the IGFBP family, which share distinct structural characteristics and functional activities. To study the binding properties of these proteins, we have expressed recombinant IGFBP-3 and IGFBP-4 using the LCR/Mel expression system. Using this system, we found that recombinant IGFBP-3 was secreted by Mel cells and had a glycosylation pattern similar to that of native IGFBP-3. Recombinant IGFBP-4 secreted from Mel cells had a molecular size identical to that of non-glycosylated native IGFBP-4. The binding kinetics of recombinant IGFBPs was measured using a solid-phase ligand-binding assay, an in vitro solution-binding assay, and a cellular proliferation assay. IGF-I bound with high affinity to recombinant IGFBP-3 and IGFBP-4 with K(D)s of <0.25 nmol. As reported for native IGFBPs, IGF-II bound with affinity higher than IGF-I to recombinant IGFBP-3 and IGFBP-4 (K(D) of <0.05 nmol). Recombinant IGFBP-3 and IGFBP-4 were found to inhibit the IGF-induced proliferation of an NIH3T3 cell line engineered to overexpress the IGF-I receptor. We have compared the binding kinetics of Mel cell-expressed IGFBPs with that of recombinant protein expressed in Escherichia coli and found them to be equivalent. Here, we show that the LCR/Mel expression system represents an effective route for expression of biologically active IGFBPs.     

Rube Goldberg goes (ribo)nuclear? Molecular switches and sensors made from RNA

Switches and sensors play important roles in our everyday lives. The chemical properties of RNA make it amenable for use as a switch or sensor, both artificially and in nature. This review focuses on recent advances in artificial RNA switches and sensors. Researchers have been applying classical biochemical principles such as allostery in elegant ways that are influencing the development of biosensors and other applications. Particular attention is given here to allosteric ribozymes (aptazymes) that are regulated by small organic molecules, by proteins, or by oligonucleotides. Also discussed are ribozymes whose activities are controlled by various nonallosteric strategies.     

A gain-field encoding of limb position and velocity in the internal model of arm dynamics

Adaptability of reaching movements depends on a computation in the brain that transforms sensory cues, such as those that indicate the position and velocity of the arm, into motor commands. Theoretical consideration shows that the encoding properties of neural elements implementing this transformation dictate how errors should generalize from one limb position and velocity to another. To estimate how sensory cues are encoded by these neural elements, we designed experiments that quantified spatial generalization in environments where forces depended on both position and velocity of the limb. The patterns of error generalization suggest that the neural elements that compute the transformation encode limb position and velocity in intrinsic coordinates via a gain-field; i.e., the elements have directionally dependent tuning that is modulated monotonically with limb position. The gain-field encoding makes the counterintuitive prediction of hypergeneralization: there should be growing extrapolation beyond the trained workspace. Furthermore, nonmonotonic force patterns should be more difficult to learn than monotonic ones. We confirmed these predictions experimentally.